Although I am well-aware that fiction anthologies of all stripes are rarely discussed here, I thought perhaps it'd be interesting to hear opinions about what constitutes a good fiction anthology. As my sig line states, I've agreed to work with the Best American Fantasy anthology series (starting with vol. 4, tentative date being mid-2011, with more information forthcoming). Needless to say, how to structure an anthology (in this particular case, a reprint anthology) and make it appealing to a large group of readers has been on my mind recently.

So, for those of you who have read an anthology or who might if persuaded, what do you look for in an anthology (interconnecting stories, particular types of stories told, lots of commentaries by the editor(s), as little commentary from editor(s) and authors as possible, themes, etc.)?