I'm all about the classes. I am shit by myself, even just practicing Hanzi. If I don't have external pressure, I just don't do it.
I go to class at my uni for free, but during holidays and when I was prepping for HSk I hired a teacher. It was a real teacher, his job is to teach chinese to foreigners, and he was only 70 rub an hour, so I thought it was a bargain.