Visual Studio开发的最佳源代码控制产品是什么？

I work in a Visual Studio/.NET shop which is still using VSS 2005 for source control. We are looking to upgrade to VS Team Foundation Server and use it's source control system, but I'm curious if that's really the best option. The creators of StackOverflow use Subversion but comment that it's a pain to merge code forks back into the main product (discussed in podcast #52). Joel mentioned that Mercurial is used at Fog Creek. Knowing that Joel is something of a software snob and he chose Mercurial over anything from Microsoft, I thought I would pose the quesiton to the StackOverflow audience: which source control product is the best for I work in a Visual Studio/.NET shop which is st