I, too, have my melee bound to my mouse wheel (click, not scroll). I just find that easier than searching for a key on the KB with my hand. I don't find that it gives me any advantage whatsoever.
HOWEVER, just like most in here and at PsB, I find binding the scroll wheel (up & down) as your attack button does give you a huge advantage over people who have theirs set to their left or right mouse button (as normal). Using your scroll wheel makes the semi-auto weapons fire as fast as any fully-auto weapon. Therefore, my clan as well as the gaming organization I work for, we consider that a cheat.
And Tabasco? There is a program called FUD Bind Kicker (From the PsB website) that can be set up to automatically kick players using such a key bind. The FUD Bind Kicker can be adjusted to kick or log anybody using any CVAR you want to keep off your servers. It's really a nice tool to have, and it causes no lag on the server. It's 3rd party software that you run remotely on your own PC. It also causes your PC no lag either....at least none that I have noticed on my machine.
I simply see the FUD Bind Kicker as just 1 more line of defense against the cheating community which should rot in hell.