I bought 2 of those for my boys for xmas. I got myself the SS kit. The ready to run models do around high 30's to 40; the SS has a 2 spd tranny and stronger motor and goes high 40's to 50. This is based on magazine reports. We haven't finished with detailing the bodies, so we haven't broken them in yet.
Just like our real cars, RC cars have plenty of upgrade options. Recommended ones include racing clutch, fiber or steel brake, 2 spd tranny, header, tuned exhaust, hi po air filter. Foam tires are supposed to be better than the stock ones. Just ordered NiMH battery packs for the receivers.
Should be a blast for me and da boyz.