I am using the new Team Foundation Service with Visual Studio 2010.
Currently I just have two users setup as the default project team. I am the first user.
I am able to assign work items to the other user. But I am not able to view his work items, or even if I can, I am unable to figure out where I can view all the work items.

In the screenshot above, in the work items tab, I only see the my work items. I can’t see all work items.
As for the permissions, I am in the following groups:
Project Collection Administrators
Project Administrators
Team Foundation Administrators.
Click on
NewthenQuery.Then select
Assigned TofromFieldoption and inValuefield select your desired user.