Yes. I rode nothing but clipless for about five years: eggbeaters on my singlespeed, Keo Sprints on my wannabe racer. Like others who've posted here, I'd thought I'd "mastered" the art of riding clipless. One of my riding buddies even commented on the speed with which I could unclip both feet simultaneously.
And then one day about three years ago, as I was climbing up the "dead man's curve" on the Manhattan side of the GW Bridge, I confronted a cyclist bearing down on me; I lost my cool, and frantically tried to unclip (and failed); I instinctively threw out my arm to break my fall; down I went, and "snap" went my arm. (Fortunately, the orthopedic surgeon installed steel plates and screws, not titanium -- "steel is real!")
Now, this didn't scare me away from clipless pedals. I still have the Keos on my fast road bike. And I had the eggbeaters on my SS when I started using it to commute last fall. But my route is short: 5 miles each way. And I got curious. What would I lose if I swapped out the eggbeaters for some decent platforms? Would it feel less "efficient?" Like Mickey85, I'd read GP's notes on pedals. So I tried the platforms. At first I was unnerved by the feeling of being unhooked from the pedals. But it took only a couple of rides to overcome that. I figured out which shoes perform best. Trust me: it makes a difference. (My favorites are Adidas Samba indoor soccer shoes for dry weather, cheap knock-off Crocs for wet.) My feeling now is that if I'm "losing" anything by having made the switch, it isn't clear what.
Let me be clear that I'm not endorsing platforms over clipless. What a tedious, endless debate! The point of my story is to illustrate what happened when I let go of some heavily marketed assumptions about what "serious" cycling involves.