I switched over to my MTB one day last week. One reason was that I was going to be riding to the college, then car-pooling with someone to get to the data center building. I didn't want to leave my hybrid locked up in the open all day long. Even though the mountain bike is technically a better bike with better components, it has a lot less curb appeal. Also, since I wasn't going to have to get up early and push hard to make the bus stop in time, I had about an hour and a half to ride 8 miles. No problem there.

After riding only clipless for about the last 6 weeks and going to platforms for a day, my personal observations are:

1) Clipless pedals are way easier to ride with.
2) Clipless pedals make cyclists "artificially" better, form-wise.

My form was horrid for the first two miles being back on the platforms. I'd bet it rivals how bad my form was back when I first started riding last year. By the time I got comfortable on them again, my form was better.

After my experience, I think for the most part, clipless pedals are a crutch. A nice, wonderful crutch, but a crutch all the same.