I just ran across this interview of Frank Jobe (the first surgeon to perform TJ) by Jonah Keri where the issues from this forum are addressed:
BP: Speaking of getting back to where you were before and getting back to elbows, we've heard from quite a few pitchers, swearing they throw harder after Tommy John surgery than they did before. Is this possible?
FJ: When a pitcher comes in with elbow problems, you often see that their ligaments were already wearing out well before. Maybe four or five years ago they could throw a 95 mile an hour fastball, but they've had that ability diminished as the ligament's been stretched. What the surgery does is restore the ligament's stability to where it was four or five years ago. A pitcher might say the operation did it, but it's just more stability in the arm contributing to better mechanics.
BP: Would a pitcher ever consider getting elective Tommy John surgery, just hoping to get that fastball?
FJ: It wouldn't help if you didn't have it before. All the surgery does is get you back to your normal elbow. You either have the stuff or you don't. A player that reaches the majors, he's spent years in the minors improving, making his mechanics better, with his muscles getting stronger.
http://espn.go.com/mlb/columns/bp/1431308.html