I've have owned the following:

Shimano A530
Shimano Ultegra SPD-SL
Crank Bros Acid
Crank Bros Quattro

Though I've heard several other people say that the platform on the Acids are big enough that you can use regular shoes for shorter distances, I was never comfortable riding them that way. The wings tend to roll forward sliding your foot off the front of the pedal. Yes, you can keep that from happening but I didn't find them to be that much better than just about any clipless pedal with regular shoes. If you're enough of a masochist you can get by with just a spindle. The SPD-SLs are probably as good or better to use with regular shoes, and they're not great.

I was pretty luke warm about the A530s at first until they broke in and started to hang in a consistent way. That allowed me to clip in 90% of the time without looking. The other key to enjoying the A530s is to use shoes with some grip, - that means rubber on the bottom as opposed to hard leather or plastic. That goes for the cycling shoes you use with them too. The SPD shoes I have are grippy enough that if I do hit the platform side by accident with them it's no big deal. I'll just pedal along until it's convenient to flip them and then clip in.