I commute a short distance -- about 2.5 miles each way, and virtually never ride further than about 10 miles from home, even in good weather. I ride a comfort bike -- a Specialized Expedition. I've added fenders front and back, a suspension seat post, and a pair of Wald rear folding baskets on a Planet Bike Eco Rack for groceries and taking stuff to the land fill. I put on Nokian studded snows for the winter, but otherwise I don't expect to make any more mods.

ETA: I forgot that I changed the crankset to get a higher gearing on the chain ring a couple of years ago. But THAT is all I plan on doing...