The other note - Photopost works with Threads out of the box - it can share the user database and login system without any hacking. The modifications here are cosmetic to share stylesheets etc... but it integrates with the user base wihtout any modifications. That's a standard part of the program.
I don't know where you're hearing negative stuff about their support. But I've never had an issue. I've had a few minor issues/questions that I posted in their forums, and they were answered.
I doubt whether it would be the industry leader that it is if support were that lousy. Install is simple - just about as easy as threads.
