If you're talking about the dual sided SPD pedals, I can give some input on two. I used to ride PD-M530s on my MTB, and did try them out in regular shoes. Not too great, pretty slippery, and the platforms definitely feel like they're made to support an SPD shoe. I recently took those pedals and put them on my commuter, and picked up a pair of PD-M424s for my MTB. Tried those out with regular shoes too, and they're definitely better. They feel almost like regular platforms.

Keep in mind that any dual entry SPD pedal you get will have the mechanism poking you in the foot when you put weight on the pedal, as the mechanism can't be fully recessed since it has to engage the cleat recessed into the shoe. Methinks that's why you see a lot of single sided SPD pedals with platforms on the other side.