It speeds up about linearly; 5 more machines will make it run about 5 times as fast, etc. For incredibly fast suites, it isn't very helpful, because the startup

It speeds up about linearly; 5 more machines will make it run about 5 times as fast, etc. For incredibly fast suites, it isn't very helpful, because the startup and sync times across machines outweigh the benefits. At causes, our tests run in about 20 minutes on 1 machine, and 4 minutes with buffet and 5.