i think it depends on the player you are going up against. I'm a 4.0-4.5.
When I use my heavy topspin forehand on my brother, it usually helps me setup a hard-hit flat forehand. He's always struggled returning my second serves that usually have high kicks on them. He's a 3.5 (used to be a 4.5 but he's very rusty).
However when i use my heavy topspin forehand against 5.0+ friends, they usually jump on it and go for flat out winners. Tried it against my hefty 6'4'' friend. he was whacking forehands everywhere needless to say I got destroyed.
Wimbledon 2004 Final. The fearless, hard hitting, fiery young 21 year old Andy Roddick.