However, the beta was exactly that, and I found that some of my favourite sites wouldn't display properly. So I decided that until IE9 is final, I'm giving it the heave-ho.
If you want to do likewise (and get IE8 back in the process), do this:
1. Open the Windows Control Panel, and then click Uninstall a program.
2. In the lefthand panel, click View installed updates.
3. Wait a moment for the list to populate. When it's done, scroll down to the Microsoft Windows section.
4. Click Internet Explorer 9, and then click Uninstall.
5. Tell Windows yes, you're sure, then wait a few minutes for the uninstall to finish.
6. Reboot your system and presto: buh-bye IE9, welcome back IE8!