I've done a few high heat butts, and find that the fat doesn't render quite as well internally. The outer parts get done faster, it seems. That said, I've had no complaints once it all gets pulled and mixed together. There just tends to be a bit more fat inside that you need to discard when you pull it. I wouldn't hesitate to do it if I had a time crunch, but I prefer to cook butts in the 250 range.