I don't have a car at all, so most of my riding is done in traffic, with lots of stops, especially downtown at "rush" hour. I've been using regular old platform pedals, because I don't have to worry about my feet at all of those intersections; I can just start pedaling. Plus, I can wear whatever shoes I want. Lately, though, I've been toying with the idea of clipless. Only three things hold me back:
1. I suspect that the performance improvement of clipless pedals is vastly exaggerated (though I don't really know, never having used them before).
2. They might be a real pain if you have to stop/start every few blocks.
3. I'm secretly afraid I'll fall over trying to unclip, and get laughed at by a fat guy in a minivan eating a burrito.