We live and breathe TFS here as I genuinely feel its the best source control product on the market. The Visual Studio integration is spot on. The web access add on give nice access for all none developers to create / edit bugs etc.
We recently have been ramping up our iPhone development and as you may be aware its Mac only using Xcode. Currently there are no TFS plugins for Xcode as it as limited (no?) support for source control plugins.
After some googling, I stumbled upon SvnBridge. This is a small module you pop on to your application tier and BOOM, you have SVN access to your existing TFS library. No mods, no hassle, just works.
Getting used to Xcode and svn can be hard work. The intergration isn't the smoothest in the world. So watch out for issues adding / removing items or moving existing items around.
Overall we are pleased with the support SvnBridge provides, day to day use works well, just a few Xcode / Svn / SvnBridge /TFS fringe issues.