It won't play over AirTunes since that's a closed (encrypted) feature of iTunes. However there are third party work-arounds for this (a product called AirFoil).
If you are using an itunes library from a shared disk (i.e. a hard disk from another computer) you have to mount an entire drive at a time, not just (say) your remote home directory. The mount point should look something like /Volumes/Macintosh HD-1/.
What's new in this version:
- support for unicode on Mac OS X 10.3
- fixed bug where songs with &'s wouldn't play.