After several months of teasing Internet Explorer's upgrade with a series of feature-free developer's previews, Microsoft has unleashed on the world an Internet Explorer 9 beta on Wednesday (from CNET 32-bit Windows 7; 64-bit Windows 7; 32-bit Windows Vista; 64-bit Windows Vista) with some impressive new features. Like any properly named beta, though, there are also some bugs to be ironed out.

This is the biggest overhaul to the browser since Internet Explorer 7 landed. The changes to the interface are enormous, the browser's overall usability has greatly improved, it's more secure, and it's significantly faster and more standards compliant.

That last point is a key issue, as the majority stakeholder in Windows browser usage finally enters the all-out war between browser publishers. What will come as a surprise to people who didn't check out the Internet Explorer 9 technical previews is that IE, long known for its struggle with standards compliance, has made serious strides in the other direction. HTML5 receives a lot of love from IE in the beta, including support for the , , and tags, and better support for DOM, CSS3, and ECMAScript5. While this may sound like alphabet soup to some, the importance can't be understated: when browser makers split on how to render code, it can make a single site look odd or function improperly across browsers.

Internet Explorer 9 beta has gotten fast, too, becoming the second browser--along with Firefox 4 beta--to offer full hardware acceleration. (Note that Internet Explorer claims it's the only one to do so, while Mozilla offers a strong rebuttal that Microsoft is overstating its case.) Google Chrome has so far implemented only partial hardware acceleration, although it has plans to complete the task.

Hardware acceleration of the variety currently implemented in the Firefox and Internet Explorer betas allows the browser to shove certain rendering tasks onto the computer's graphics processing unit (GPU), freeing up CPU resources while making page rendering and animations load faster. These tasks include composition support, rendering support, and desktop compositing.

JavaScript plays a major role in the Web, and Internet Explorer 9's new Chakra engine combined with the GPU acceleration gives the browser some serious rocket fuel. On WebKit's SunSpider 0.9.1 JavaScript benchmark test, IE9 beta averaged 379.4 milliseconds over three cold-boot runs. On the same Windows 7 computer, Internet Explorer averaged 5,236.6 over three cold-boot runs, nearly 14 times faster and just a hair slower than Chrome dev 7.0.517.5 and Opera 10.62.

The new Add-On Performance Advisor takes the IE8 feature of exposing add-on load time and warns you if a particular add-on is slowing down your browsing session by more than 0.2 second. You can adjust that time to one of several presets from the same menu that you can disable an add-on.

Internet Explorer aficionados have mostly likely already seen screenshots of the interfaces when Microsoft's Russian subsidiary leaked the look a few weeks ago. The interface has undergone an enormous change, following the trend of minimizing the layout to maximize screen space. Microsoft takes an interestingly different approach than its competitors, which placed the tabs above the location bar. In IE9, the tabs reside on the same row as the location bar.

This results in a cramped feel that other minimalist interfaces avoid. It may work for some people, but the experience suffers from an otherwise unnecessary shortening of the location bar and a limited amount of space available for tabs. If you only have a handful of tabs open at a time, you might not mind. If you're the kind of user who runs dozens of tabs simultaneously, you might want to consider becoming a different kind of browser user if you can't let go of your IE addiction. It quickly becomes difficult to distinguish multiple tabs.

The interface isn't the only part of IE9 that's gone back to basics. Notifications, such as the session recovery warning shown here, appear at the bottom of the browser window and won't "grab your focus" and prevent you from continuing to browse. (Credit: Screenshot by Seth Rosenblatt/CNET)

Besides that drawback, IE's new look is quite usable. The stop and refresh buttons have been shrunk to take up as little space as possible while still being visible. It's a bit curious that Microsoft didn't combine them into one, as other browsers have. The cramped location-and-tab bar could use all the extra space it can get.

Most items in the Command bar, such as print, page controls, and safety controls have been collapsed into the redesigned Tools menu. Only the Home button and the Favorites button retain their own top-level icons. As with other browsers, the status bar is hidden by default, although it and the Command bar can be re-exposed by right-clicking on the Tab bar.

The new Tools menu is highly usable, as well, with a clean and simple layout. The Internet Options menu, on the other hand, could desperately use some font resizing and re-organizing, because it's a chaotic mess of options that are hard to read and harder to find.

Firefox fans will no doubt enjoy that IE9 has a larger "back" button than "forward," mimicking Mozilla's browser interface.

Internet Explorer 9 is crammed with new features. One of the interesting concepts implemented by Microsoft is a reversal of the current trend to make the browser the operating system. Internet Explorer comes with some natural-fitting Windows 7 integration. In IE9, you can pin specific sites to your Windows 7 desktop taskbar. Click and hold on a tab, and drag it to the taskbar. The site's favicon will become the pinned site icon.

Developers who take advantage of the options available to them for Pinned sites can customize the Windows 7 jump list for their site when pinned, or add in special features such as an unread count for Web mail or media player controls for streaming audio and video sites. (Credit: Screenshot by Seth Rosenblatt/CNET)

Pinned sites by default re-color IE9's Aero glass-style interface based on the color schemes in the site's favicon, which is a neat little trick. If coded properly, a site can customize the jump list links. You can currently see what this looks like if you pin to your taskbar. I didn't see thumbnail preview media controls in action, but Microsoft says that the feature should be available to sites that want to implement the API. Pinned Web mail sites, for example, will be able to show in-box counts on the Windows 7 taskbar.

IE9 takes Internet Explorer's tab sandboxing and gives it Chrome-style "ripping," so that you can drag a tab to create a new browser window. IE's tabs allow the user to rip them off and immediately Aero Snap them to either side of the browser, useful for looking at two sites simultaneously.

Again, like its competitors, Microsoft attempts to re-brand the location bar thanks to bolstering it with search features. Internet Explorer's "OneBox," as the company is calling it, combines the search box with the location bar. You can navigate to a site, search for sites, or look at browsing history or favorites. You can also change search providers at the bottom, which is a slick merge of the old search bar functionality into the location bar. By default, the OneBox won't remember your keystrokes. If you let it, though, you'll get additional search suggestions.

Notifications in IE9 have taken on an entirely different look. Small and minimalist, they appear at the bottom of the browser and don't stop you from browsing. Tab sandboxing will not only prevent a single tab crash from taking down the whole browser, but IE9 will ask if you want to resurrect the tab, too.

A new "New Tab" page lets you resurrect closed tabs and previous browsing sessions, as well as provide large versions of your most frequently-visited Web sites' favicons for quick access. It feels a bit empty and lacks deep customization, but it's a step in the right direction. It's appreciated that when you mouse over a site's favicon, you're told how in general terms frequently you visit the page. Annoyingly, IE9 lacks a radio button in the Tools menu to make about:Tabs, the new tab page address, your default home page. You can type it in manually, which is certainly easy but not effortless and makes the page just a bit harder to reach.

Following up on a report from earlier this year that toolbars and other add-ons were a major source of instability in Internet Explorer, IE9 keeps a stern eye on your add-ons and will warn you when one is unnecessarily slowing down your browser. (Credit: Screenshot by Seth Rosenblatt/CNET)

The new Download Manager incorporates reputation-based security, to accelerate the pace at which you can install a new download if not speeding up the download itself. This means that well-known files, such as installers from trusted vendors, will cause fewer warnings if any to pop up.

Other bugs
However, at least in my experience on a laptop running 32-bit Windows 7, I found Internet Explorer 9 beta to be shockingly unstable. Despite restarting the computer, uninstalling and reinstalling the browser, and closing all other running programs, IE9 beta crashed with disappointing frequency. It was too frequent to believe that Microsoft would release a beta that was so wobbly, but the browser would freeze on me when opening tabs, closing tabs, switching tabs, adjusting settings, or performing searches.

It's likely that this has a lot to do with the multitude of software that I install and remove, but interestingly I found the session recovery feature on the IE9 new tab page to be more than effective at resurrecting whatever tabs had been closed.

This first beta of Internet Explorer 9 continues Microsoft's trend of pushing out betas that are highly usable. Despite the inevitable hatred that the browser will attract, it's a solid build, with interesting takes on existing feature-concepts, and some others--such as the reputation-based security--that hopefully competitors will take note of. It's worth downloading and checking out for the great strides Microsoft has made in speed alone; along with the snappy design and standards compliance, Microsoft may have finally gotten IE right.