I'm currently working with mingw. I use it because it works of of the box in QT SDK and since I'm lazy, I really don't want to spend more time configuring another MS tool that I not using. It allways worked fine for me. Sometime ago I asked in this forum the real diferences between mingw and MS compiler. Some said that probably mingw generated bigger librarys and probably somewhat slow, altghout I really don't believe, each case is a case and should be tested individually. Probably MS compiler is much more popular and gets better support.
Other projects use it, I believe Octave, a very big and very nice project also uses it.