I gave it a spin for a few hours.
I would say it's... unremarkable. It's like it tries to play so exceptionally safe with everything that it doesn't take any risks. That's the kind of feeling I get from it. Also, for some reason it actually doesn't "feel" like there's a million billion customization options.
For example, in terms of character design... costumes are limited to side chosen. This makes sense, but the amount of costumes available for each side is limited by this. Especially for the security team. In fact, even though there are quite a few options for appearance... they kinda boil down to the same archetypes and I just don't feel that any one design I have is very different from any other.... which kinda defeats the point of being able to customize. I would say the reason for this is simply because everyone is actually TOO diverse. Compared to TF2 in which the amount of customization is actually so limited that you instantly recognize differences in player appearance; in here, everyone kinda just blends together into a grey mass. There's also not enough hats.
In terms of guns... Bleh. I don't want to say this but I think 70% of the guns are virtually identical. Even the add-ons aren't very impressive. It actually lists it right there on the add-on "all add-ons of this type are identical". There are minor differences between the weapon types but come on... all the guns even look the same! When I die in other shooters, I go "oh man, that guy's gun looks so awesome I can't wait to get it". Here I go, "oh look, he killed me with generic gun #7. I don't even know which one that is other than it shoots bullets."
As for gameplay and the rest? It's a generic shooter what else is it going to be? The parkouring thing is actually barely noticeable. I don't know if it's because of poor map design or something. It just isn't very noticeable. The only move I actually use in actual gameplay is the slide. Occasionally I'll try to jump around to reach someplace. Key word here is try. More often than not I'll fail to do so because it turns out the parkour thing doesn't work on a certain prop or what have you.
Well, there you have it. That's my impression of Brink.