Open in Google Chrome works like the other engine-switching plug-in for Firefox, IETab. Apparently, OGC was based on the same code. However, if you're familiar with IETab, which renders pages in Firefox using the Internet Explorer engine, be prepared for OGC to behave differently.
Instead of rendering the IE page in a new tab in Firefox, OGC opens the tab you're switching in Chrome itself. Now, since Chrome is significantly faster than IE7, the URL should open fairly quickly. At least, it did for us during multiple tests. Still, this was a jarring experience at first because it takes you out of the Firefox window. Also of note is that the extension requires you to manually point it to your installation of Chrome.
We weren't fond of the interface, either. To use the plug-in, you must either use the context menu or customize a toolbar with a Chrome button on your own. There was no Menubar option for accessing the add-on's options, either. For developers who need to switch quickly between browsers or users who are playing around with Chrome, Open in Google Chrome should prove useful. Beyond that, it's not much more than a curiosity.