This is a good question, because we actually were using Hydra for a while. We ran into a lot of problems where hydra workers would just hang once they finished

This is a good question, because we actually were using Hydra for a while. We ran into a lot of problems where hydra workers would just hang once they finished their test (used strace to see what they were doing, and it looked like they were stuck in some sort of infinite loop). Hydra caused enough headaches that we just stopped using it; out of that frustration, Buffet was born. We tried pretty hard to make Buffet 'just work' and stable.