I'm currently playing around with a bunch of various themes on my local dev box, hoping to find that one that jumps out at me as "Cool!".  In the mean time, I'll stick with this one, as I like how it separates the categories from the rest of the post.  Whatever theme I use permanently will do the same.  I've got a couple that I'm converting to BlogEngine.NET themes as I find time.  We'll see how it goes, but they look nice!