Having a gi class added to my schedule has helped me a lot lot because Im tall and skinny, so i get paired with guys who are generally a lot heavier than me. Training with the gi, at least from my experience really forces both parties to rely more on pure technique than on strength and power, and you therefore become a better competitor. Just my two cents.
Anderson Silva (MW)
Randy Couture (HW)
Quinton "Rampage" Jackson (LHW)
Roger Huerta (LW)
Karo Parisyan (WW)