I'd say TFS is more than just source control. If you can afford it, I would definitely advise to use it. When you start using Team Builds for example, or using stuff like Work Items, then you'll see that TFS can really manage your whole development life cycle, providing a rich environment in which reporting, ease of use, slick VS integration and solid source control are all rolled in to one.
It does require some iron on the server side. I do not find it to be slow however, it works nicely over VPN and supports offline work.
A major con is the install process (on the server side) which is tedious, non-flexible and in my mind (I come from a field in which packaging up apps and deployment are very important) a bad example of how SQL Server, Reporting Services, Sharepoint and webservices could be installed.