Here here, that's what I want to know too. I was shocked it was available with the initial release of the iPad and for me it's one of most sought after features. Granted, the iPhone doesn't have it, but I never missed it. However since the iPad is a wi-fi device and I use it strictly within my house, I would expect it to act like my MacBook and recognize my shared iTunes library. C'mon Apple, get with it.
My most sought after iPad features:
1. Folders (same as it was for the iPhone pre-iOS 4)
2. Multitasking (even more important on the iPad than my iPhone)
3. AirTunes support (see above)
4. Retina display (as great as it is on the iPhone, it will blow everyone's socks off on the iPad and I could use the extra resolution when reading text)
5. Tabbed Safari browsing - the current method of switching between open screens is clunky and some kind of tabs feature would make a lot more sense
6. Printing - check

7. FaceTime - I don't need it, but it would be incredibly awesome to have.
8. CoverFlow in iTunes - Why isn't it there already?
I'm sure there are others but those are the ones that I think of the most.