Currently, it's very obvious Amarok 2 is in the alpha phase. The major thing that changed is the interface, which looks nicer and more modern now, with the collection browser located in the left and the playlist itself located to the right side of Amarok's window.
I installed Amarok 2 using this guide from the official website, on a Debian Lenny with KDE4 installed from SVN (not complete, only kdelibs and kdebase libraries).
The center space is empty, unless you add a widget. Widgets should be a nice addition to Amarok: some of them include a Wikipedia widget or a Last.fm widget. The only thing at this point is that neither of them work. But since this is alpha, I didn't expect them to. I'm sure widgets will be one of Amarok 2 strong features when it will be released.
Incomplete at this point
The Tools menu is poorer than Amarok 1.4, featuring only the Script Manager, the Cover Manager and the options to scan and update the music collection.
I couldn't make Amarok to output any sound, but that's probably because my KDE4 installation is not complete (I only installed kdelibs and kdebase from SVN - if that has something to do with it).
Both the script and cover managers look unchanged since the 1.4 version.
What can I say. It is alpha and it surely looks and behaves like alpha. I don't think Amarok 2 is anywhere near a final release, and there will probably be months until we'll have a first stable 2.0 release. Until then, I'm glad to be blessed with the solid, full-featured 126.96.36.199 version, which will be around for maybe even 6 months to follow. The two features I can highlight at this point in Amarok 2 are widgets and a brand new interface, which definitely looks nicer but will probably suffer changes, since it's not very practical.
Updated: Jun 16, 2008 (Created: Jun 16, 2008)