People in this thread are obviously only talking about their own experiences with spin n gos, limited experience which leads them to believe one or the other thing.
There are professional spin n go players, so IT IS PROFITABLE if you are good enough. At the higher spin n go levels the rake is 6%, and at 25c and 1$ spins it's 8% rake. But the higher rake at the micro stakes spin n gos is made up for by the terrible players that reside there.
I have played a few hundred of the 1$ spin n gos over the last few months, and I think I'm up between 50-100 bucks on spins over this time. I might obviously just be well above the EV, so if you ask me what I think about spin n gos I will say: Play them, they are awesome! Again, as I said, the answer will be different depending on who you ask.
Spin n gos is a hit for me for 3 reasons: They are fun, fast, and I get to practice short handed play, which is always an area you'd want to improve in your holdem game