Tom:
The big problem with TT4 is when you hit your brakes it disables the traction control system. The Differential are different than older trucks and do not allow you to BTM the truck. In 2003 they did not eliminate TT4, they just altered the diffs so that you could use BTM, TT4 or also the rear locker. The best off all three worlds.
I have seen many talented drivers use TT4 with out a problem. In order to use it correctly you must keep your rpm steady and not jump on the gas. Many off the hardcore H1 guys have added lockers to the front and rear.
If you dont plan on doing heavy duty off roading I would go with the TT4 truck.
Mark Weber
Webman
www.wisconsinhummerowners.com