I have had posts marked to expire, and they don't expire. Makes me look stupid when outdated information is left up on my website and customers see it :-( As it turns out, this may be caused by a feature I wouldn't expect to use - the expire to category option. If you have a category checked, (which was in my case, although I didn't check it -- perhaps a default?) the post doesn't actually expire. I'm thinking a few interface and/or documentation changes would resolve it and get a higher rating from me.