1. An admin can login as a user through the user management page.
2. Not currently, you can restrict how many pm's any user is allowed to have though.
3. Yes, see the Who's Online box to the left and its details link.
4. umm, view the post, click edit, then edit content, then click submit, thats 3 clicks (including clicking in the textarea)... If you delete a post it dissapears but its children (responses) are left (unlessyou delete the children).
5. Member management in the control pannel allows you to search by ip.
6. There is both a FREE irc addon (using pJiRC and creating a channel on one of the many millions of free irc networks) and a Raidersoft (raidersoft is nto free) addon at
UBBDev.
7. Mods can remove access to regular members, edit posts, and delete posts; as well as approve posts in any forums that reuire moderaton that they have access to.
8. As long as the client uses html links the link should be clickable.
9. You can rate both users and threads.
10. There is currently no integration modifications to integrate with other services, you could request (or hire a developer) to make such an integration. As it looks like you're looking for a payment addon, the UBB will be coming out with one in one of the major releases (at this point it doens't look like 7.1, so you'd be looking at 7.2 at the earliest).
I cannot validate on any type of diskspace usage, as I don't use vbulletin; i can say however that the UBB uses a caching system to provide less of an impact to the server, unlike other products.