Have some feedback!
I took a quick flyby in your map and some things caught my eye. (I'll others some bandwidth by posting them as links instead of pics)
http://i.imgur.com/m11ouQal.png
First of all, the "obvious" route from spawn leads to a flank. Walking straight towards the nearest building eventually leads to the flank path down. Basically, it makes the flow feel clunky.
http://i.imgur.com/HhYBxRm.png
The fastest way to mid is to go left from spawn. This really feels odd, as you'd expect the flank route to be there. Making the ramp on the left more attractive would really help the map flow better. Just another thing to consider.
http://i.imgur.com/jIsQI9bl.png
It's good that you have these soon-to-be crates clipped smooth! Also, there's a mysterious lamp sticking out from the ground.
http://i.imgur.com/x7Ln2sSl.png
The indoor areas might be too confusing for some. The turns you take inside really disorientates the player (especially at this ramp here)
http://i.imgur.com/yWxVkEFl.png
http://i.imgur.com/9XKh2ZJl.png
http://i.imgur.com/RwFiC7Pl.png
Some ceilings are a bit too low (under mid and on the top floor indoors)
http://i.imgur.com/yMIwBMAl.png
The bounding walls could be raised a bit, just to make it more obvious that you can get there. For instance, at mid, when you stand on the container you are higher up than the walls. Raising them temporarely makes it so much more obvious not trying to rocketjump over them. It also help with...
http://i.imgur.com/iGM0tUal.png
Optimization! Though it's a bit pointless to point this out at _a1 but I believe you render the whole mid from here, which may or may not cause some unnecessary lag. The frames won't drop on an empty server, but given 6-12 players being rendered with their unusual hats on point, the frames may dip a bit.
http://i.imgur.com/ZrHsMNOl.png
Just to nitpick some more. I see a nodraw here!
Do submit this map to a gameday/imp sometime. I'd like to try it out to see how it plays.
This is not a must, IMO. A bit of asymmetry, as you have in your map, is fine in my books!
There was two medium combos at middle + a small and a medium health kit, which I actually think is too much! Elsewhere, I don't know.