I haven't tested every last feature as of yet, but have not come across any issues with IE8. I won't do a full, 100% regression test with IE8, but there are many TD users already using IE8, and no problems specific to IE8 reported since it was released from beta. Additionally, you can uninstall IE8 and return to IE7 should you have any problems. (I've tried the IE8 uninstall on Windows XP and it worked without issue.)