I'm as big a fan as they come, but live Cocteau has a problem -- there's just one Elizabeth. On studio albums, as you know, there are numerous vocal tracks, creating a rich, layered sound. I never knew how important this element was until it was gone. Live recordings (including the BBC Sessions) just feel sort of anemic, because only one melody is being sung. Yes, her voice is still beautiful, but it changes the nature of the songs.
I'm not going to tell anyone not to listen for themselves, but I was disappointed.