I just updated my PC to Windows 8 and have been trying out IE 10 along with that.
One issue I did encounter is that I could not use the "enter" key to create a line break when typing in the message editor on some forums.
If anyone else is having this issue here or on any other forums, for that particular forum (well, this is how it works for here and other vBulletin boards):
Click "Settings" in the upper right corner of the page
Click "General Settings" on the left side of the page under My Settings/My Account
Scroll all the way to the bottom under "Miscellaneous Options" and make sure "Standard Editor - Extra formatting controls" is selected and NOT "Enhanced Interface - Full WYSIWYG Editing", which will cause you to not be able to create a line break with the enter key.
Hope that might help somebody until the internet catches up to IE10.
Edit- There might be something that Tony can change later with the board as far as making it "more optimized" with IE9 on up, but this workaround works for now.