Any comments? What I've read seems to favour direct radiators. I've never had dipoles nor listened to them for more than a few minutes in various stores (never with music).
However, bipole/dipole designs will probably work fairly well with "ambient" multichannel mixes that attempt to recreate the ambience of the venue/studio by simply adding reflections (or audience sounds) in the rear channels.
But direct radiators are the recommended speakers.
Do you mean dipoles like Magnepan or Martin-Logan? These are highly regarded as some very musical speakers. Unless you are talking about the rear channels only, then I would say direct-radiator rear channels are preferred for multi-channel music.
Direct radiators to be sure, and you don't want the rears up high either. Your best bet is on stands such that the tweeters are about the same height as the front L/R speakers.