In response to another thread where it was a side discussion, let's discuss the topic here.

I'm in the anti-clipless camp because I don't want extra crap to lug around. I usually commute in street/office clothes and don't want to have to worry about another set of shoes after I arrive at work. (I can't really fit them in my 20 L backpack, which is the largest size that is really usable for a multimodal commute with a subway, train or hovercraft).

I also commute in heavy traffic as shown on other posts and don't like my feet chained should the bike get hit/slip/fall on rained-soaked roads.

However, what is the big advantage to them? People say they're faster, is there any empirical data out there?