Internal geared hub with coaster brake. Hit as many pot holes as you like and the brake pads still don't rub. Change gears at stop lights. Never hear "honey, my chain came off again."

For me the only downside is cost. You pretty much have to build a custom wheel. You can't just use any old shifter you might already have. Gotta buy the matched shifter.

OK, the other downside is gear range. But, unless you live by mountains, you don't need it. I've taken the front derailleur off of my geared bike.