pgoat

I've used evertything from BMX to mtb to road to hybrid. no recumbents or shock equipped mtbs or penny farthings....well, you get the idea.

when I lived on Long Island and had nice smooth roads I preferred a flat bar road bike or a hybrid with 700c wheels. On long open roads you want the bigger wheels with narrower tires to limit your rolling resistance. If you are really getting creamed by wind and the traffic is not in your face 100% of the time, by all means get drop bars.

In NYC I prefer the MTB. I ride a rigid 25-ish lb. bike from the early 90s. I like that I can dab with my foot easier when I zip between stopped traffic and knowing it won't be as bad if someone smashes their chain into the frame when lock up next to me. I cringe when I think of that with a wafer-thin AL road bike brame.....and yes i see people do it all the time (not to my bike, luckily....)

The keys for a commuter imo are durability, theft prevention, safety and ease of maintenance.

For the first, I go with a heavier frame - str8 gague is fine.

2. - an older uglier bike is better if you lock up outside.

3. I prefer a straight bar with mtb style brakes. I always use bar ends to give additional hand positions. If you prefer road bars just get those new light weight secondary brake levers (mounted on either side of stem) for tight traffic spots.

4. Single speed is great if your ride is flat. For so-so hills I run one chainring up front and a rear casette with a big enough granny to get over the top. Ditch the front derailleur if possible. Hub gears are okay but heavy.

I say stick with your mtb and just put some good 1"-1.5" slicks on there and pump 'em up nice and firm. Get bar ends to stretch out and give your hands a break. if your shifters and gears work well your speed will be fine for the commute.

If you were buying a bike to commute I'd say look into a hybrid. They are the best all-rounders imo.