I can't help but wonder. Was Wil always an asshole, or did exposure to the speds (and let's be honest, he got a lot of unwarranted shit flung at him over Wesley that, in all rights, should've been tossed at D.C. Fontana and the other TNG writers) make him one? God knows, if I got crapped on like that when I was sixteen I'd probably develop some serious issues.
It didn't help that de Lancie's Q, despite being a monumental pain in the ass, also had an amazing amount of panache and style. I mean, come on, he gets downgraded to mortal, has to face his own death, eventually redeems himself, and his first action is to return to the bridge of the Enterprise with a fucking mariachi band and stick cigars into Picard and Riker's mouths.
Yes, Q was a smarmy dick, but damn if he wasn't entertaining.