Put this up on the beta server and played it. It was actually pretty fun. The gameplay with the low barrels in the middle worked out pretty well (lots of crouching and arcing balls over to hit people). Crouching under the forts was fun, too.
Since the short barrels look kind of bad, I would just scale the entire barrel down (32 units tall, radius of 12, scale texture by .5). It would also allow you to be able to move in between the barrels under the forts, which would be nice.
Some of the bunkers in the middle need the border textures rotated. Also, if I recall correctly, the windows were too low to provide much cover while standing, but too high to shoot through while crouched.
On the top area, some of the boxes are too close to the wall -- looks like you can walk by them, but you can't.
Only part I don't like is the base - it's way too easy to defend the flag, as there's only one tiny opening to get to it. At the moment, most people are distracted trying to jump up the pillars, but if people play it seriously, getting a flag capture would be almost impossible.
Visually the map looks OK, but adding some natural shapes to the rocks so everything isn't just all flat walls would help a lot.
PM me if you need the login for the beta server so you can play test your map.