I race my truggy on 5s. I like it a lot. I also did some practice laps with 6s, much faster, but still controllable.
My transmitter comes with this new trigger thing that's just come out. It lets you vary the throttle input to the car while your driving, instead of having on off power. It's quite amazing, it lets you drive a fast, powerful car without having to use full power all the time.