I'm surprised to see this thread is still alive. Tennis tips is much much better reading than anything in pro discussion.
I thought I'd just repeat myself and say topspin is vital at the highest levels. No pro can hit the ball and have it land in without topspin, not even the Del Potros. It's also an extremely effective tactic at both pro and amateur levels in a consistent, baseline game.
However, it is completely overrated and overused by people lacking footwork, technique and/or power. I just saw my nephew play. He uses a western grip, completely open stance and WW forehand. His favourite player is Nadal. >_>
I swear I could hear his wrist dislocate a little more with every shot.