<p>We have a small 3 developer team that is currently using Subversion for our source control. We expect the team to group to 8 members within the next 6 to 12 months. We are considering changing our source control to either TFS or Mercurial for improved branching. I know TFS is overkill for just branching, but that is the immediate need, and the other features of TFS could aid our team. One of our main concerns with TFS is we've heard that there is a lot of overhead deploying it, especially on a small team. I'm hoping to get some community insight into just how much overhead there may be involved, suggestions to make the process easier, and anything else the community may feel is useful in making the decision to implement.</p>

It's been awhile, but I'm thinking that it takes about a half-day to get setup, plus some time reading the manuals beforehand to make sure you know what you're doing.  Configuration doesn't take too long -- you need to add all of your developers in as licensed users.  Setting up projects is not too hard.  I usually set up AD groups to map on the project roles and add those groups to the appropriate roles.  I set up a new project in about 1/2 hour.
Note: I don't use any of the features of TFS except source control.  If you plan to item tracking, use the project sharepoint site, etc., your mileage will vary quite a bit.  I've found that on our projects (2-3 developers) a wiki works just as well for project management.