I owned this instrument for quite a while some time ago, but ended up selling for reasons described below. I'm a songwriter guy, so that will reflect on my review.
I'll start with the PROs:
The dynamics and round-robins are great, this might be my all time favorite kit in terms of feeling "alive" when you play it. At times I had some issues with keeping the dynamics in a certain range, but that can be solved by setting the response curve.
The sample quality is outstanding, NI and Abbey Road are sure 2 good companies.
The room mics sound lovely, definitely add to the "alive" feeling, I liked the control over mono and stereo room mics for various applications.
The CONs (for my specific situation):
Being a song writer, I want my instruments to load within a certain time range, so they are ready when inspiration strikes. Due to the long loading times, I found my self often waiting for the VST to load, so I wouldn't recommend this as a songwriter tool.
I couldn't manage to make the drums "sit" in the track. I suspect this might be due to the specific sound of the gear and room used @ Abbey Road. Whatever I did with the drums, I never was happy with the result as they wouldn't blend well with the rest of my recording. I never experienced this issue with another drum library, I tried my best, in the end I just became frustrated and sold it.
Again, this one might be my personal taste, but I couldn't find a basic, generic, bread and butter snare drum that would fit my music. They all sounded kinda fancy, but I couldn't find a basic, ol' pop-rock snare drum, or at least not the kind I was looking for. Again, I never experienced this issue with another drum instrument.
At the time I owned this product, the cymbals and snare drums couldn't be used between the 2 provided kits. Meaning, if I liked the cymbals in kit 1 and snare in kit 2, there just wasn't a way to use them together. I found this incredibly annoying, knowing the ride I like is there, but couldn't be matched with the kick I liked.
Routing and working within Kontakt was cumbersome and left me frustrated from time to time.
I don't really think MD is a bad product, the quality is definitely there but I think a potential buyer should take the above mentioned CONs into consideration before buying. Maybe watch a youtube review or at least listen to the samples on NI's page.