Why the year round qualifier? That's a tall order for people in cold climates. The people who commute in the winter tend to be the enthusiasts.

Anyway, outside of winter I'd say at least 10% of the staff in our office commute by bike on a regular basis. Probably 1/3 to 1/2 use bikes with drops. Of those that commute regularly in the winter (about 3 of us), 2 of us use bikes with drop bars.

Not statistically significant I suppose but it would seem to refute the idea that drop bars and commuting don't mix.