We have also just started migrating away from sourcesafe and Bugtracker.NET to TFS. The install was fairly painless, except for a couple of pre-reqs I missed when I read through the install guide.
1) was that the data-tier needs to have analysis services in the same instance. Having waited for a kindly DBA to do the necessary (the data-tier is a clustered server and was already hosting production stuff), I then found that you could install with analysis services seperate, but only by using an answers file.
2) was silly of me, but I had forgotton to install reporting services on the app tier. Again an answers file will allow the reporting services install to be elsewhere.
The other thing was while I was migrating source safe. We have a lot of shared files in sourcesafe. I knew that TFS doesn't support sharing so we had already decided how we were going to deal with these shared projects. I then migrated then over to TFS but I didn't migrate them from the location in sourcesafe that they had originally been created in. The migration only took the history from the time of the share into that location. Which meant I had to delete that attempt and do it again, but pick the share of each project that had the most useful history on it.
Inspired by another answer on here, the security admin side is a bit confusing to start with. You have to seperatly control TFS, Sharepoint and SQL Reporting Services permissions. It doesn't help that this is my first experiance with the admin side of Sharepoint.
Team build has been slightly more frustrating. But we hadn't had a build server before, so there is some learning going on. I am currently trying to get database projects to build correctly, think I have got there, agian it was just sorting out the pre-reqs required. Some of visual studio, bit of SQL server, found a patch for the DBPro for team suite that means I don't need SQL server any more!
Nothing much else to report. Just getting used to how the TFS sourcecontrol works. So far it is WAY better than source safe. I haven't yet thought "why did it do that?" which was often on my mind when using Sourcesafe, particularly early on before I had learned its odd ways.