from SoftwareUpdate description:
iTunes 4 features superior sound quality including support for MPEG-4 AAC audio. iTunes 4.0.1 includes a number of performance and network access enhancements, and only allows music sharing between computers using iTunes 4.0.1 or later on a local network (in the same subnet).
Looks like apple got enough pressure from the "the Big Five" and removed the option to share over iNet ... dammit, i really liked that feature, and not just because of the obvious hacks, but because it was great to have my library available everywhere ... a sad day
(mods, sorry, wrong forum, saw the sticky too late, please move)