When I did an R20 build, I did coaster in the back and drum up front. Liked the setup a lot, especially after jumping off freewheel bikes where I was used to brakes at hand -- kickback shifting and getting used to a coaster brake again was a very short learning curve, but not what I'd come to consider natural.

Today, I just rode in on my lockup beater, which stays in a rack at the bus/work end of a bike-bus-bike commute -- an old, rusty Schwinn Super LeTour with a S2C wheel out back, no front brake. It's a fairly upright bike; gearing is medium and low; I only use it for the three mile, regular commute. Coaster brake is fine, don't miss having a front brake, and since it stays locked up through nasty New England weather in a coastal town where they salt the roads, I'm not sure I could get away with zero maintenance and hand/rim brakes.

Your setup would depend on your use. Casual bike with upright ergos and fatter tires, I'd go with just the coaster brake. If all the other bikes your ride have hand brakes and this will be the only one with a coaster brake, I'd consider a front brake -- also, the skinnier the tires, the more you should consider a front brake. If this will be geared high with a more aggressive, forward posture (bullhorn bars?), and especially if you will be running skinnier tires, I'd be thinking freewheel setup with rim brakes at both ends.