Yo, I use my mpc2500 in conjunction with Mbox2 and PT 7.4 (PC) and it works great. It took me some time to find the good workflow, but i do it now like this:
I make the beat in the mpc and record every track or instrument in different tracks in PT trough the digital SPDIF cable (Digital out makes a 1:1 copy of what comes out of the mpc into PT, and i found out it doesn't mess with the swing of your beat once its recorded in PT.)
Make sure you set your mpc to start, before playing your beat, with a click intro.
Allign the clicks in PT by zooming way in.
All your recorded tracks will now be in sync.
It takes up some work but after all this you can edit and mix your beat properly and fully controllable.
Another very important thing: Find some good plugins to mix. I would say find the McDSP plugins (eq, compressor) for low latency and great quality!
Peace!
(if anyone has some tips to improve on this workflow, please give me feedback!)