I've got Shimano A520 tourers - swiped off my geared bike. SPD on one side, flat on the other. I very rarely use the flat side (and definitely wouldn't recommend it for riding fixed) but in terms of design they work well either way.
However if I was starting again I'd probably go for double-sided Time clipless and have different pedals (or a different bike!) with straps for riding in trainers. Only takes a couple of minutes to swap them over.
http://www.londonfgss.com/thread9986.html
I've got Shimano A520 tourers - swiped off my geared bike. SPD on one side, flat on the other. I very rarely use the flat side (and definitely wouldn't recommend it for riding fixed) but in terms of design they work well either way.
However if I was starting again I'd probably go for double-sided Time clipless and have different pedals (or a different bike!) with straps for riding in trainers. Only takes a couple of minutes to swap them over.