Assuming most people commute on the road, how many gears do you need? I have a 21 speed mtb being converted to commuter (until I wear it out and decide what I'm buying next) but really only ride it in 7 gears (and could get by with maybe 3 or 4 of them). I assume a bike set up with only 3 or 7 speeds would have a wider range of ratios and work even better.

Thoughts? I'm slowly building in my head what I want my next bike to be like!