Actually, I was rather intrigued by the possibility of controlling certain features with aftertouch (perhaps brightness/timbre going up as I press harder on the keys and so forth), so I'm definitely interested in at least playing with it, but I thought maybe I missed something as to where they could be obtained.
The X-Custom addition to the library is for people who want to customize their controllers. It allows users to have custom control over volume/timbre MIDI assignments and dynamic range thoruhg the assignable slider in the Player. This feature is especially useful for users with Wind Controllers. Also, this is particularly helpful for people with certain sequencers. For instance, Logic 6 (and earlier) and GarageBand users have the reset to "0" bug which this addition will allow you to reset the controller and avoid. With the X-Custom Folders, please note that all instruments load at full volume rather than the minimum volume standard used in the Dry and Wet Audition folders. This is useful for people with Standard MIDI files they want to play or with particular sequencers as well. Most users will not need this optional addition.