This post is going to be a bit negative. For users looking for Enterprise features in the first version of Windows Phone 7, I think I have to recommend wait.
The Office Tab
- No out of box support for SharePoint 2007
- No Windows Authentication (NTLM) for SharePoint 2010 - you will need to activate Forms Based Authentication
- Same issue as previous Windows Mobile 6.5 in requiring a personal certificate to connect to your corporate Exchange. I understand this is more secure, but when you could easily integrate with Facebook, Gmail and Hotmail but can't connect to your corporate Exchange it is a bit silly
On a positive note, the WP7 browser is excellent and renders both SP2007 and SP2010 perfectly.