Spin & Go's Can Be Profitable
While it is true that the rake and variance are huge on Spin & Go's, I've run my bankroll up several times playing them. That's because there are a lot of inexperienced players playing them. It will take some time to learn player tendencies/leaks and how to exploit them, however.
I wouldn't recommend Spin & Go Flash though. It's tougher to beat the high rake with one-minute levels and 15bb stacks to start with getting shorter every minute, so there's very little room to outplay your opponents. Beyond the 1st level it becomes a push/fold game (in most cases) and you need to know those Nash Push/Fold ranges pretty well to break even or make marginal profit.
However they're fun, and I do play them at $0.25 sometimes when I'm bored.
Also, I wouldn't recommend playing Spin & Go's with ridiculous multipliers like $1 for $1M, since a large portion of your buy-in will go for the large multiplier (unless you like playing the lottery). I noticed getting 2x multipliers on $1 Spin & Go's at a very high frequency recently, then I realized what was going on. I contacted
pokerstars yesterday asking for info on the
odds about $1 Spin & Go's and they've yet to reply.