I am facing several major issues with IE10:
1. Autocomplete does not work for most sites unless one switches to "compatibility view". I am unable to save usernames, passwords and form data in normal mode.
2. When I login to the Gmail web interface, I am unable to delete messages in any folder (Spam, Sent & Trash) - they keep reappearing. However if I login from a Win7/IE9 machine, I am able to delete messages without a problem.
It seems to me that IE10 (Desktop) on Windows 8 has major compatibility problems with many websites.