Oh, and I found that videos recorded on a Nokia (really sorry, but I forget the model - a recent candybar model, the one with a camera on the front) can't be played over bluetooth (must be due to the speed of bluetooth - it's nice that the 770 realises this and stops you from trying anyway and getting appalling playback performance ).

You can copy them over easily enough and play from the memory card/internal memory (i.e. I can confirm that the bundled 770 video player supports the format without having to convert/transcode etc).