My problem(s) with TT.
It's hard to play TT hard unless you hit a set, but I find you almost have to raise PF with them. If you raise, and hit your set, the board has most likely given your opponent at least 60% of a broadway straight. (due to people calling with AK, AQ, AJ) If your raise gets multiple callers, and there's another face card on the flop, your set can be in real trouble.
So many times, I find my trip-tens beaten by a straight. The only time they seem to make money is when I can play them as an overpair.