How many times has Andy come back from 2 sets down to win the match? A fair few I'd think! Those matches would have been lost if they'd been 3 setters!
Would they really though? Surely as with the five setters Andy would've upped his level and found a way back. I'd be interested to see his win-loss record from losing the first set in 3 set matches, particularly in the masters tournaments.
With that said I personally love the longer matches in the grand slams and hope they never change to 3 sets.