All of the things mentioned plus a whole lot more have
already been requested on the Betaplayer forum. There have been no major improvements to the PPC version of BP because Picard is currently working on the PalmOS version (plus holding down a real job at the same time) which is now ahead in terms of features. Once both versions have reached 1.0 (at which point the name will change to The Core Pocket Media Player) the feature set will be identical and presumably they will be updated in parallel.
With regard to AMR audio support, it is already requested and is working on the PalmOS version so it will not be much longer until it appears for PPC. This is clearly an important feature for Smartphone users so rest assured it will be added.
JohnDaddyo: The same could be said about WMPs inability to play anything but Windows Media files (MP3 being the only exception), personally I can't see the point in Betaplayer supporting a format that everyone already has a player for already. Also bear in mind that WM support worked fine until Microsoft changed the programming interface rendering BP's playback broken.