The question I have always had is not so much "do you pull up", rather "how much efficiency is actually gained by pulling up". If I have my 215# body pushing down on the downstroke, how much extra am I really getting out of lifting the other foot?

You can really experience it in spin class when a real cyclist-instructor takes the class up to 120 rpm and holds it there. Your legs need to work together maintain a nice smooth stroke without bouncing, and you need positive control during the upstoke.

I like both, clipless for fast bikes, platform for everything else. Switching back and forth is a little dangerous at first, you tend to forget the proper muscle motion coming to a stop.

Each has its place; I wouldn't ride platforms 20+ and I wouldn't wear clipless commuting or sightseeing.