1) As for difficulty, it was similar I guess. Get used to pushing yourself to do well on them, preparing hard for any of those practice tests will translate into better MCAT scores.
2) The TPR tests were much more math intensive than the actual MCAT. When I took the MCAT last August there were maybe 5 questions in the PS section that required any decently difficult (like all those scientific notation operations) math. I found also that alot of the VR questions were different from the MCAT. Like the MCAT questions (and you can sorta see this from the official AAMC practice tests) were more retrieval and main idea based, while TPR's questions were alot more based on interpretation (and I found the interpretation questionable at times).
Note I'm probably making too big a deal out of nothing. I took TPR, studied hard all Summer out of their books, attended all TPR classes, and ended up with a 37 with no other real preparation.
Good luck!
