I think that having your foot attached results in more balanced muscled development and less strain on legs/knees/ligaments than you would get if you are just limiting yourself to using the muscles that allow you to push downwards on a platform pedal (probably not a big deal for shorter commutes but over a season of daily riding it would make a difference). I just tried eggbeaters for the first time and found them to be far easier to get in/out of than I expoected and much easier than the toe straps/clips that I have used for years. I'm an instant convert! Wow.