I used to be one too and the answer is of course you tip the pizza guy. This is like asking, "Should I tip my waiter?" It's not like it's an open debate; there is a clear societal contract that pizza guys get tipped. You just do it, hot/cold, long wait/short wait, good pizza/bad pizza; that mother er needs to be tipped and if you don't do it, you're a big time asshole who's not just spitting in the face of that particular pizza guy, but rather the face of the entire service industry and the faces of tipping customers everywhere.