Haha, to read this thread, you'd think the hangover was a mythical beast. Like a leprechaun.
I'll come clean. I've had some rough hangovers from time to time. I know how EtOH is processed biologically, and yeah, yeah, drink water before bed. But seriously, one of the side effects of knocking back a few too many is a lack of discretion for future consequences.
Echoing other people's sentiments here, it's an age/time/quantity thing. When I started drinking, I could roll out of bed fresh as a spring chicken. Now, I never know for sure how I'll feel in the morning. So, if I want to be productive in the morning, I'm abstinent.