I love drop bars in traffic. It depends on what I'm doing, but on a flat stretch of road, I ride the hoods. Downhill, I hit the drops and either pedal hard or tuck-n-roll. I rarely use the flat part of my handlebars unless I'm trying to position myself higher to look around or something. Since my STI levers allow me to brake from either of my two main hand positions (I have a few derivatives of these positions), I do kind of like drop bars over flat bars for commuting.
Flat bars aren't too bad. I do notice a little more wrist/hand fatigue on longer commutes, though. I could go for some barend grips, but it doesn't bother me enough to spend the cash on them. Sometimes I just cup my palms around the handlebar ends when I know I won't need to brake.