I can't really speak to performance (I don't have any large projects where I could tell a difference), but the install is painless, and the windows git shell is really nice.

I've been using msysgit at work for the past couple of years, and it works fine. There's a bit of an impedance mismatch between the command line orientation of git and the crippled command line experience on Windows, but msysgit comes with its own mini bash implementation, complete with ls, vi and a few other handy utilities.

windows git performance on a 300KLOC, 8000+ file C++ project was IME very good - and that was 2-3 years ago. compared with g++, it was great.