I agree with OverLoad and Lastrep72. If TexR is trying near the weight he used on the Smith machine with regular flat benches he is only inviting a maybe long term injury. That 'aclimation' may take a lot longer than one thinks and can be misleading. A regular bench is more of a 'S' curved push for most guy's. With the position on the Smith, there is a fix, straight unnatural push away from the body. I think of shoulder joint and tricep tear first thing. (actually a better way to do flat benches is with DB's that follow the natural twist of the hands/wrist/elbows, shoulders...but than again, to me, BB's are more fun)
If any one feels comfort using the Smith machine, than help yourself. If you do decide to switch to regular benches than select a much lighter weight in the beginning process. Your muscles are learning a whole new way of pressing and are getting adjusted to a different position of weight loads during the exercise, on them. Caution though, not matter what one may believe, the Smith machine is not a perfectly safe piece of equipment. Should have someone watching you for those last few hard reps. Good Luck.