Looks like IE7 is going to be released on November 1st via Windows Automatic Updates. I personally haven't installed any of the beta's or release candidates yet, but from what ive heard its going to be "teh awesome". I'm actually really excited for the new version and am thinking about switching back from Firefox.
As an ASP.NET developer I have always tested my projects with IE, but then I browse the internet using Firefox. There's nothing really wrong with that, it would just be nice to actually build sites and test them using the same browser which I use to browse the internet. Of course I realize that I can easily test/debug my apps using Firefox as my other colleagues do, but its usually a corporate initiative that the our sites must support IE so I usually choose it to debug with.
That being said, I have had a number of recent issues with Firefox (start up times, freezing, updates and restarted automatically, etc.) and will probably try to use IE7 as my default browser. The only thing I think ill miss in Firefox will be my cherished Mouse Gestures plug-in.
If you don't to adopt you can install the Toolkit to disable the Automatic update for IE7.
Check out the IE blog for the latest and great info. I would at least recommend that you check out this post for more info about IE7 readiness and adoption.