Clipless, IMHO, is completely not worth it on a commute/errand bike or if you ride in urban areas. There's not enough open road to get the benefits of clipless, but you get all the hassles of having to clip in and out, and you have to do it more often. Plus the shoe thing. I use SPDs, so I can walk around just fine, but it would necessitate bringing a second pair of shoes.

I'd put clipless on a fun-only road bike in a heartbeat, but probably just BMX pedals on an errand bike. I should add, though, that I went straight from platforms to clipless. The movement necessary to get out of cages is not exactly intuitive for me, and would probably have been more dangerous.