FLAC for sure.
Internet Audio streaming (I took a first cut at it, and got a working proof of concept going, but I can't do GUI coding well). Streaming MP3, realaudio, etc.
Support for streaming FROM other Centrals. (Put those 3 centrals to use!)
Record from Audio in. Think TiVo for FM/AM radio.
Support for more mobile devices, at least the ability to copy music to flash/mmc/sd cards.

Price really is what killed the Central. Any new version needs to be near the price point for a TiVo machine.