I like them because the classic blog look is horrible for quickly scanning a site's homepage looking for interesting articles to read. It forces the latest post to always be an absolute killer to draw new homepage visitors into your site (note: some A-list bloggers achieve this anyway).

I dislike them though because it increases the development time for new sites and (sometimes) increases the time per post as you deal with all the extra post backend stuff that goes along with a lot of them.

But overall I think they're a great thing for self-run sites/blogs in general.