I should expand upon my thoughts, because I find your post stirs me to consider my opinions.
In my opinion, honestly, I don't think this building is any kind of remarkable masterpiece, or anything. It is, as you say, a glass box with some panels and a notch. It isn't in any notable way different from countless similar buildings in other cities (it looks to me like it could just as easily be in Uptown Dallas). It's a nicely executed, professionally handled glass box with some panels and a notch, but yeah, it's not all that original/striking.
I do like it, though, as while it is not in any way remarkable, it's also not in any way (that we can see) awful. It's the very definition of a "background building," which is exactly what it should be IMHO. It fills a dead space in the city with something that is perfectly agreeable if not strikingly original/beautiful, and it makes things better for its presence without calling a ton of attention to itself in some kind of solipsistic "look at meeeeeeee" fashion a la a starchitect building.
What's more, if the info we've got so far on its pedestrian interactions is accurate, while as a piece of design it's not all that remarkable, it does seem to be doing everything right in terms of what a building in an urban setting should be doing first and foremost: it's enhancing the public realm and making people want to be around it. It'll have nice wide sidewalks, engaging ground floor businesses and interactions, etc. That aspect of the development gets it a lot of brownie points in my book, as it's easy for an office developer to skimp on such things, particularly when the building is outside of the active core of downtown and in a part that is, honestly, just as dead as the dead parts of other cities we say Fort Worth has a "better" downtown than. I appreciate that the developer and designer are going the extra mile to do the right thing (while "the extra mile" should, in fact, be the norm, it very often isn't - witness the nothingness that is the ground floor of nearby Cantey-Hangar Plaza, etc. - so I applaud them for it all the same).
And also, another way I like the building is that while it's, as I've said, not really all that remarkable or interesting as a piece of design, when placed into its context it comes across as more interesting. It's got great historic buildings in close proximity, plus a '60s tower that's not all *that* bad (500 W. 7th) and a brutalist piece of garbage over at the park that towers above all else, both of which are very "concrete-y." So in that context, this glassy notch box is kind of like a splash of cold water in the face, like a '60s International Style glass box can be. It's refreshing. Now, I'd hate a huge stretch of buildings like this - it'd be monotonous and repetitive and dull - but as an accent here and there, I enjoy the contrast.