I typically use 3 gears, but when there are hills or something I'll use a lot more (and even then I shift less/later than I should). But for my mostly flat commute, I'm good with 2-3 gears and just mash/spinout/coast rather than change because, well, I don't have much more top end and it rarely occurs to me. I'm working on being better about that though. Well, I guess I sometimes use 4 if there's a slight incline when I'm stopped at a light. But my commute is pretty flat except for a pedestrian bridge over a highway where signs say you should walk your bike (and I do most of the time).