Bought it this weekend, here are my thoughts:
New sampler is fantastic. Much improved on the old version and can be little to complain about.
Tracker is 50% genius, and 50% confusing/lacking. The fact it works is incredible and it seems pretty good at picking things up. Being unable to slide the detection point around means if it just isn't detecting something its hard to get it exact, and there's some confusing crossover between detection features that seem to have similar effects. Seemed stronger on kick and snare than hats/OH/toms where it struggled a bit.
The included samples...... I'd imagine they're pretty useless for 99% of people who visit this site. I hate the kind of "one size fits all" approach where they presume a few plugins can transform a blandly recorded kit into something for any genre. The room they tracked in is enormous and is pretty noticeable on the OH mic tracks. All the room mic options are enormous and frankly way too big for most drum tracking situations. Its more like a concert hall than some of the classic drum rooms previous SDX's have recorded in in the past (Henson/Avatar/Hit Factory/Warehouse/Blackbird/Grandmaster/Sound City). The tunings are generally too high/pingy/choked for my tastes too. Being able to mix & match sounds is nice, as is some of the processing options to control the envelope, but it almost feels with this library that you have to go in with the intention of getting your hands dirty to get something exciting out of it. Not the philosophy I'd go into a drum tracking session with at all.
I'll most likely delete the included library as I can't think of a single situation where it'll do a better job than an SDX I already own. The sampler itself is great, so I'm happy enough just paying the upgrade price for that. Hoping future SDX's change their philosophy completely though, I think honestly they've dropped the ball here.