I said a little about it last year
on the blog, but nothing terribly profound. Having played around on Pandora since then, I think it functions best as a personal background radio with the added bonus of zero Chris Moyles and Russell Brand. Whenever I've tried it, it's only brought up things I already know (and like), or no-name limp imitation stuff, which I just skip.
I was at a conference once where an idea similar to Pandora (may have been Pandora itself, I don't remember) was presented to a room of computer music techies. One of the examples played was 'Rimshot' by Erykah Badu, which relies heavily on the bass riff from Miles Davis' 'So What'. The presentation showed a bunch of ways in which the system might categorise the Badu track, but made no reference to Miles; so in the questions I asked - and was met by a stunned silence. The guy presenting hadn't made the connection (OK), but more to the point hadn't even thought that this sort of thing - actual musical correspondences that you can pick out and hold in your hands as it were - were relevant to organising music - even though this exact procedure is how so much music is made (how the Erykah Badu track was made, certainly). The system abstracts into musical categories that have increasing irrelevance (Cale's 'extensive vamping' puts in him the same box as Count Basie, surely!), rather than historical/compositional categories that actually reflect the material world of music creation and reception - the link between Cale and This Heat makes more sense this way, eg.