I for one have absolutely no idea how to get seperate .kde / .kde4 directories when building KDE 4 / Amarok 2 with kdesvn-build rather than using Kubuntu packages. If someone could enlighten my (I already asked the people in #kde in IRC) I'd be delighted.
Besides that, I'm sure that Amarok 2 will rock our socks off. Maybe in the near future I'll find some time to help out with a bit of hacking.