Just played this in today's imp and had a pretty good time. Definitely feels geared towards 6s classes, which may or may not be a problem depending what you're going for.
One of the things I noticed is there's a lot of unused space. A couple of rooms just seem really big for no reason. Here are two examples.
This route is great for Scouts, Soldiers, and Demos, but nobody else can even access it. I'd maybe put a ramp from second up to it a la Process so Medics and other classes can utilize it.
Another example of catering towards jump classes. They have the option to go
over this incredibly cramped route, which other classes are forced to go
through it. I'm also not a huge fan of vent routes, but if you're going to keep it, I suggest making all the classes have to use it. Otherwise you're punishing people for playing something other than Scout, Soldier, or Demo.
Feel really vulnerable on mid. Feels like you're trapped in a box with no idea of when you're going to be attacked. I understand adding cover, but it makes the player feel trapped and more susceptible to splash damage. If you want cover, one option would be a roof of some sort. That would help players find cover from Soldiers using the upper route and also make mid more dynamic.
Edit: One more thought to add. This is your mid! It's where a lot of fighting will happen. Make it memorable! A cool option would be to mimic the building you have covering last. It's unique and would solve the problem with feeling blind, while still providing cover. Just a thought.
In the few rounds we played, I didn't see many people using this route. Seems like it's intended to be a flank, but even then the door leading to the point seems a little narrow. I might open that up a little bit.
Last bit I have for you. This looks like a great little jump for Scouts, but it's not! I need like 8 more hammer units before I can crouch jump up there. Make it happen!
Hopefully some of this is useful and you can incorporate it into the map. As I said earlier, had quite a bit of fun, but I was also playing as Scout/Soldier the whole time.