I have a VXL Rustler and the best thing that happened to me was when I had a wipeout causing one of the leads to the motor to become disconnected, and this "forced" me to upgrade the stock ESC to a MM...

, I have since installed a UBEC and this enabled me to increase the battery to a 4 cell, and then I went to a Feigao 9L motor (2700kv) and gear up a little. With my setup the ESC runs a lot cooler than the stock , and the motor a fair amount cooler