I went on a 16 mile greenway ride today using my Ergon pedals for the first time. I can only compare them to cheap platforms and SPD clipless pedals.
They do grip. I wore plain Nike sneakers/trainers, and there was no movement, sliding of my foot. To reposition it, I had to release almost all pressure on it. I did not have to physically lift my foot up off the pedal, but I was not pushing down on it at all.
I found them comfortable. I was worried with the contoured design that there would only be one "right" position, but that wasn't the case. I was able to shift my feet around and still be comfortable. (I was just experimenting, but with my foot injured, I wanted to be sure that if one position bothered it, I could try another position, and I could).
I am pleased with them, after a limited trial. The next test will be when I get on the road at higher speeds, but I don't see anyone's foot slipping off these pedals. I also found that I don't miss the "improved efficiency" of clipless pedals. I really don't think I was utilizing the upward pulling capability of those, anyway.
Grits
2010 Trek 5.2 Madone WSD, SI Diva Gel Flow
2002 Terry Classic, Terry Liberator