The concept and functionality are simply amazing. For the way I work having recorded every player individually is a huge advantage over just a soloist and a2 samples. With the latter you are in all sorts of trouble if you want to score a choral with four independent horn parts, for example. For me Modern Scoring Brass has the concept got right.
Unfortunately I am not too happy with the sound personally.
For example, compare these shorts articulation sounds:
The Modern Scoring Brass example does not sound good to my ears. It simply doesn't. True, you could use eq and reverb to mask it (and for that example you would definitely add some reverb in a real usage situation. It's actually great that Andrew didn't to show the sound of the library). But if you don't happen to like the source sound (which is the case for me here), there is only so much you can do. You can't transform it into something else entirely. It's interesting how different these two sound, given that both used a scoring studio as recording location. Cinematic Studio Brass sounds much more refined and full here out of the box.
Another thing I didn't like too much from the walkthrough video: in my opinion the timbre changes very little throughout the dynamic layers. The crossfade is very good, there is no phasing I could hear. But the tone of the instruments changes too little for my taste. Brass instruments are capable of a great variety of timbres. And I didn't hear that captured in the walkthrough. For example here:
cc1 moves through the entire dynamic range of the horns. I actually do like the sound of the horns here. But the timbre sounds quite unfiorm to me until it reaches fortissimo. Also from the video it seems that the library has only three dynamic layers (p, mf, ff), which is not much for brass, especially since the top layer has the distinct brassy timbre.
While I do like the concept very much, I am not digging the sound from what I have heard so far. Let's see if that changes when a more in-depth look at the various articulations of each instrument is available.