The only downside I've seen is that a few days ago the wus weren't running as nci and were taking over cores, not allowing other wus to run. Not everyone got the bad wus, I did and have dropped it back to only running on my raspberry pi's. Prior to that I had been running it on multiple instances on most machines, but the problem I mentioned caused the processors to be over committed. That problem seems fixed now. When it's running right, it's all good, but the project does have more than its share of difficulties and the admin seems a bit lost when it comes to fixing the problems. Still, it's free credits most of the time.