I have been using IE9 from beta, to RC, and now I am on the RTM version which shipped last night. I really, really like IE9. It is crazy fast, and very secure. While on the beta version – there where a bunch of websites that I had trouble with – but enabling compatibility mode usually fixed them right up. Most of those issues I am not seeing in the RC or RTM version.
They also fixed it where you can change the location of the tabs so they can be back on their own line – which I really like:
Check out the product comparisons: http://windows.microsoft.com/en-US/internet-explorer/products/ie-9/compare-browsers
With full hardware acceleration – this browser really screams. I am loving it.