I'm using a Hitec HS-5965MG. Not high-end as far as price goes, but plenty fast enough for me. Some of the guys are using high-end KO servos, but they tell me that they turn the rate down as they they are too fast?
I've stuck with Hitec as I've never broken one. I used to use their 645 servos, and they took some serious abuse without complaint. Bit slow for carpet racing, though.