Trying Internet Explorer 7 beta 3 on Windows XP SP2. Not as bad as one might expect. Quite a few Firefoxisms (from the tabs and RSS support to the “Find More Add-ons” mechanism). Some features are rather well-implemented (for instance the pop-up blocker in the add-on bar) and it seems like its performance is decent on a very fast connection. Despite my opinions of Microsoft, this version of IE seems quite decent. Actually, it seems to be the one browser which works appropriately with the Categories box in WordPress. Neat.
Disparate 
Thanks for the warning. This is not a primary machine for me so it was just a trial. And it’d be hard for me to replace Firefox and Flock, especially with things like Scrapbook and the Google extensions. It’s just nice to see what’s there. Opera 9, Safari, Camino, etc.
I’ve installed IE7b3 on another computer, and it’s a lot smoother-running than the previous beta; I also like the improvements made. As long as Firefox has the extensibility factor in its favor, I won’t even think about switching to other browsers. I like all the extensions available that add functionality no other browser can offer.
Until Microsoft can figure out all the major bugs in IE7 (which might not be until its final release), I never recommend installing it as a main browser. I’ve had a lot of people complain to me how it destroyed the computer’s dll library during uninstallation.