Limping is definitely a mistake if the villian is too tight. Why give him the chance to see a free flop and hit a monster? Also, you have got to vary your play or someone will get a read on you quickly. You can't simply limp with good hands and raise with marginal hands because the opponent will notice and stick in a reraise everytime you raise and check to hit when you limp. Heads up you are playing so many hands with only one person to pay attention to...it is impossible to hide under the radar.