At least for some (including me), IE 7 has not worked. See
microsoft.public.internetexplorer.general.

This program clearly has more than its fair share of problems.

The newsgroup has not been helpful in dealing with issues.

The microsoft phone help number is so busy that they ask you to call back
later.

Most (but not all) have been able to uninstall it (through the control
panel) and return to IE 6.

While it may well work for you without any difficulty, be aware that this
upgrade clearly needs a great deal more work and waiting may be the best
course.