The idea is that you pay for broadband and then get to share as much music as you like (legally). The broadband connection magically reroutes your sharing traffic to it's own servers, thus keeping tabs on what you're doing.
If you're "not bothered" then this is probably a reasonable deal (although it's expensive broadband, so you'd need to use it quite a bit to make it worth it). If you are bothered about your own online freedom and privacy, then steer clear of this. The fact they're filtering your internet connection and "diverting" some of it means they're not working like a normal ISP (who generally have charters saying they'll pass anything along without discrimination). Think about it: What if they decide to divert your iTunes traffic, or your webmail server traffic?
They're apparently responding to people's "need" to use filesharing (Kazaa, eDonkey etc), rather than downloads (like iTunes, Napster etc). However, this seems like a terribly invasive way to do it. Surely most people will just stick to iTunes/Napster and illegal filesharing?
Once again, it's clueless music industry people being clueless. Or is it?