I tried out IE9 but I didn't like what they did to the favorites section, I'm very happy with IE8 and I coudn't wait to go back to IE8. I couldn't find IE9 in the program list to uninstall it, so I did a system restore to a time before I installed IE9 and brought back IE8.
I hope we don't get forced into using IE9 because I just don't like it at all.
It's there in add\remove programs you just have to click "view installed updates" to see it.
In case I didn't like it myself I prepared an image before installing IE 9 beta.
My initial experience was a dismal failure with frequent crashes.
I finally pinned down the problem to the realtime protection provided by a Spybot Search & Destroy plugin.
Turning off (disabling) the plugin fixed it.
The plug in was somewhat redundant since I have Javacool's SpywareBlasters host file protection as well as running
IE 9 in a sandbox (Sandboxie).
I like IE 9 especially since I found out how to get the menubar back.
It's faster than IE 8 by a mile and even faster than Firefox (at least by my tests).
Chrome and Opera are faster but I suspect the final release will close the gap somewhat.
Having said all that my favorite (read default) browser is Firefox 3.6.10 to be replaced by FF 4 when it goes gold in all likelihood.
BTW I don't see MS forcing us to switch to IE 9 at least in Win 7.
Maybe the next version of Windows but by then there will probably be a new version of IE.