Here's a cool video courtesy BloodyElbow.com that shows current UFC welterweight champion hitting mitts with Manny Pacquiao's boxing coach (and coach to countless other boxing greats) Freddie Roach.
The video doesn't show a tremendous amount, but it seems clear GSP is utilizing Roach's skills to tighten his boxing fundamentals. There appears to be an emphasis on economical motion, short but tight punches, ring generalship, timing and perfecting simple but high percentage hand combinations.
Frankly, I suspect GSP could avoid training with Roach altogether and still best Jake Shields at UFC 129. The present-day difference in standing ability is already enormous. But credit to St. Pierre for continuing to develop his skill set, knowing the long line of contenders at middleweight will require a heightened focus, heightened commitment. Who am I to say GSP will walk through Shields and take Anderson Silva's title? No one, but the likelihood of that outcome is high and at a minimum, amusing to ponder.