hello! I'm loving the game so far but i have a few issues
first off, it's kind of hard to know how fast you're going and the speed lines definitely don't help. it's not that i don't like them it's just they're very inconsistent. for instance if you run normally then there are no speed lines but if you crouch Slide going the same speed then they suddenly appear and it's the same for moving midair. I say you just have them appear at a certain speed rather than to make the game look more cinematic.
second, the amount of air control in my opinion is very... limited? I'm hesitant to type "none" because that would be a falsehood but it (again in my opinion) is especially useless when you've just grenade/shotgun jumped. But that's more of a pet peeve than an issue. I suggest doing something Source engine esque where you can sort of steer your momentum. I don't think I'm describing this very well so I'll link a wiki page on what I mean here. (EDIT: be sure to look at the videos i'm not suggesting that you put in the exploit just the air control, the beginning of the portal 2 video is a good example)
Finally here are some minor but annoying issues. accidental wall slides happen all to frequently in tight spaces, and it even happens while crouched. holding down shift while moving forward prevents you from jumping ( never mind it was just my keyboard.) Sliding into enemies in tight spaces is unreliable and the grappling gun's string doesn't always connect to the surface that you're shooting at hovering a few feet off the wall (visual bug only)
Keep in mind this review ONLY contains issues, do not let this discourage you from playing this awesome game!