Speed running in this game is super fun. My favorite levels are the ones with little to no enemies where you can just speed run as fast as possible with no interference from unpredictable AI. My brother and I are constantly racing each other back and forth, trying to beat the others score by a couple milliseconds.
Things that need tweaking
Wallrunning Wallrunning needs to be less forced. So many times I'm trying to get through a door or drop down to the milk and I can't because I'm stuck on a wall. I think it would be far better if you only wallrun while moving towards the wall, or at least if you could drop with crouch.
Enemies It's incredibly frustrating to be zipping around at 60 mph, and slide right past a dude faster than he can blink, only to get shot in the back of the head. Perhaps if turning reduced their accuracy? That would fix that and make sense. Also, getting caught on a ragdolling enemy is really annoying. If you could walk through them once they're dead, that'd be nice.
Things that would be fun
Some more movement options could be fun. Maybe poles you could swing off? Zip lines? Portals? Some different enemy types would be interesting as well. A juggernaut guy who takes two hits to take down, or a sniper who hones in on you with a laser if you move too slow. More weapons too. A vacuum gun that sucks enemies and barrels towards you and has negative recoil, or a sniper rifle with massive recoil but very slow reload.
These are my times. Best ones are Tutorial, sandbox 2, escape 2, and sky 2