The JR 3550 is what most of the racers run at our local track. It's fast, centers well and is nice and compact.

MAKE SURE you run a good servo saver on it though, I'd also recommend carrying a spare gear set...just in case. The gear sets are just basic nylon and they're inexpensive...better safe than sorry.

I'm running a JR3550 myself and I BEAT THE CRAP out of it...and I haven't had any trouble...but I still have a spare gear set just in case