I have been riding with clipless pedals for the last 5 years. I started out with shimano-SPD compatible pedals and then 2 years ago switched to crank brothers pedals. 3 years ago the thought of moving back to non-clipless pedals would never crossed my mind; even on my fixed-gear commuter, I had SPD clipless pedals on. I began using platform pedals on my fixed-gear about 2 and one-half years ago. I ride everywhere with my fixed-gear bike, even on fairly hilly terrains, and I didn't find riding with platform pedals to be any slower (granted the non-coasting nature of the fixie no doubt helps with the rotation of the crankset on the up-stroke).
I have since contemplated using platform pedals for my nice geared bikes. Although I like clipless and my biking shoes are comfortable, I want to be able to ride my geared bikes with normal shoes sometimes. Although there are dual-purpose pedals out there, I find them to be unattractive and a poor compromise.
The final straw is probably the noise factor. The clipless pedals I have used all began to make squeaking noises after a while, even though the bearing might be OK still. I am annoyed by the ever-present squeaking noises when one rides, especially when climbing or riding spiritedly on flats. After sunday's ride, I decided to go back to quill pedals. I have a pair of SR road quill pedals sitting around. I overhauled the pedals and attached power grips to them on my Rivendell Romulus. I am going to see how they do, and decide whether I want to go "clipless"-less on my Ebisu, too.
I will probably keep my crank brothers around, just in case I want to use them sometimes.