In Live 8, if a drum rack had more than 16 sounds and I scrolled up to the 2nd set of 16 sounds in the rack, my MPD18 would automatically follow - ie it's 16 pads would always match the sounds listed on screen. In Live 9, this no longer works, no matter what the screen shows, the MPD triggers the 1st 16 sounds. Not sure if this is a big or something done on purpose, but it's really annoying. I like to use Slice to MIDI for experimenting with samples, and this has made it a very large pain in the ass.
Trap music is not supported in the current version.