I'm as big a fan of Ubuntu as anyone, and I'm glad to see Dell supporting a MS alternative. However, the absence of a fully supported Linux version of iTunes prevents me from adopting Ubuntu as my primary operating system.
Have you tried the new Ubuntu One Music store? It's not bad to start with and is rapidly improving. Plus offers cool features like cloud storage of your music collection (ultra-portable, take your music wherever you go).
Run a VM with Windows just for iTunes.
I used to do that, but I think now the better recommendation is just to ditch Apple. My HTC Incredible is a great phone, and I love Amarok.
Having just switched from Amarok 1.x to 2.x, I'm underwhelmed. But as a linux user I have never used, nor needed itunes.