Updated, June 17: The sandboxing of plug-ins, such as Flash, in Safari 4 will be limited to users running Mac OS X 10.6, which will be available this fall. The feature is currently not available, nor will it be available to Windows users. Windows users should also note that changing the default search provider is limited to either Google or Yahoo.

The public version of Safari 4 was released Monday amid all the iPhone noise at WWDC, and Apple confirmed what those who played around with the beta version already knew: Safari is now a serious browser for serious Windows users, and its position on Macs has been bolstered.

You can download Safari 4 for Windows and Mac from CNET Download.com.

If you're unfamiliar with Safari 4, I strongly recommend checking out Stephen Shankland's analysis of the Safari beta version that was released in January. The biggest overall changes are the graphics improvements, including the new interface and the new JavaScript engine called Nitro, but since the beta little else is dramatically different.

Users of Safari 3 will be hard-pressed to not notice that the interface is completely new, with a look and feel much more in line with the other major Webkit-based browser, Google Chrome. The browser launches with the menu bar, tab bar, and status bar all hidden, presenting you with the location bar, bookmark bar, and the slick Top Sites interface. Top Sites is essentially Opera's Speed Dial feature, presenting your most commonly visited Web sites, with a Cover Flow-style skin. The black background, curvature, and reflective window bottom make this the most professional-looking Web browser around. A blue star and an upturned corner indicate that a site has been updated since your last visit to it. Tap the Edit button in the bottom left corner to remove a site or pin a site permanently to Top Sites.

One major change to the interface from the beta involves tabs. In the beta, Apple experimented with a Chrome-style "tabs-on-top" that it has abandoned in the public release. The font for the tabs was often hard to read, and made Safari look excessively like Chrome. The new tab style now looks much like the old tab style.

Safari's visual speed dial is one of the new browser's best features--if your system is new enough. (Credit: Screenshot by Seth Rosenblatt/CNET)

Cover Flow is now available as a graphic way to browse your bookmarks and history, however, if you've got a somewhat older computer you still won't be able to use any of these graphics improvements.

Another new change for Mac users in Snow Leopard will be the sandboxing of browser crashes caused by plug-ins such as Flash and Shockwave. The page that they're on will continue to function, and you can reactivate the plug-in by reloading the page.

Safari 4 is also the first nonbeta browser to fully complete the Acid3 Web standards compliance test.

The URL bar does feature "smart" surfing, but only for including your history and bookmarks--much like Internet Explorer. Chrome and Firefox remain the only browsers to default to Google's "feeling lucky" style of searching from the location bar.

Cover Flow in Safari gives your Bookmarks and History a graphics lesson. (Credit: Screenshot by Seth Rosenblatt/CNET)

Apple's big claim with Safari is that it's the fastest browser on the market, and Apple just might be right on that count. On an Intel Core Duo T400 ThinkPad, with 3GB of RAM and a 2.53GHz processor, I ran both Webkit's SunSpider JavaScript test and Mozilla's Dromaeo test on Firefox 3.5 Preview, Google Chrome 2, and Safari 4. Safari came out on top in Dromaeo by a long shot, but Chrome eked by in SunSpider.

For the SunSpider test, Chrome hit 597.0 milliseconds, while Safari scored 620.4 ms and Firefox comparatively chugged along at 952.2 ms. On Dromaeo, Safari reached 175.06 runs per second, Chrome managed 67.92 runs/s, and Firefox came in last again at 48.48 runs/s. However, Chrome only led in two categories, and it tied both with Safari. Safari definitively led in 36 tests, and Firefox led in 12.

Keeping in mind that although these tests are affected by background computer processes, your hardware, and other factors, Safari is definitely one of the fastest browsers out there. However, it still lacks extensions, and for many Firefox users that's enough to keep them from switching. Even Internet Explorer supports some form of extensibility with its Web Slices and Accelerators.

Like many other browsers, Safari's location bar offers suggested sites. (Credit: Screenshot by Seth Rosenblatt/CNET)

Safari is still a RAM-devouring beast, too. With two tabs open, one to Dromaeo and one to SunSpider, it was using a shocking amount of RAM--more than 500MB after running both tests. Google Chrome consumed about 75MB of RAM across the same two sites under the same circumstances, while Firefox required 120MB.

With about 8.5 percent of the browser market, it's clear that Apple is positioning Safari as more than a developer's tool on Windows, and that its successes at building a faster JavaScript engine should be taken seriously even with its other drawbacks.