I noticed 3 major issues the first is clipping, and I totally get why you wouldn't have done this yet but seeing as its your first map you will probably miss a lot of clipping spots if you don't get on top of it right away. The second issue is sloppy brush work ie. the floor is misaligned in several places (if you'd like i can take a screenshot of them but since there are at least 10 of these so I held off for now) and I'm sure your aware of your water not really working properly. The last problem is the limited access to the control point for the less mobile classes and limited access to useful perch points in the mid area (although you may have this on purpose it doesn't lead to fun game play for a lot of people who will likely complain). All that being said I really like where you are going with this and can see a lot of potential in the layout keep at it.
edit: also i wouldn't bother making it look pretty yet if i was you but that is up to the individual