Is there even a decent Windows shell extension for git yet? When using Windows and teams not already familiar with git, Mercurial + TortoiseHG was an easy choice.
Msysgit is what I use and I really enjoy it. Git also has a Visual studio plugin now you can use if you prefer GUI to CLI.
I don't know enough about mercurial to offer a good opinion, does it offer something equivalent to hooks in git for setting up custom behavior?
I don't know if it's decent, I'm a Linux user but there's TortoiseGit:
http://code.google.com/p/tortoisegit/
Current version is 1.6.3.0, so looks like it's considered stable enough to be beyond the 0.x-stage... ;)