I've been playing about with exporting video then putting it all together in Adobe Encore. Unfortunately the video quality from a straight export from Flash (possibly down to my limited knowledge with such things) is very poor and the performance of Encore when it comes to actually creating the DVD is ridiculously slow.
I've tried a couple of third-party swf to video converters with much better visual quality results... but they both failed to include the sound.
PITA