You can see that it's one of your first maps. That's why I don't want to post detailed feedback for now. I think the general stuff is more important for you and your next maps.
First one ist that you really need to avoid large and open areas. The game can't handle it well and it results in a bad gameplay with lags, etc. Look at other maps and how they're built. Almost all maps where it's possible to look from flag to flag or from base to base are bad.
Second one is the lighting. Try to avoid light entities, it looks very strange without a light source. Use some of the light textures for the tunnels and caves and add a nice sun lighting for the sky. You can find default settings for the sun lighting here:
http://dplogin.com/forums/index.php?topic=714.msg221412#msg221412Next thing are the flags. Don't place them at all places you could imagine them. Decide what place should be the base and where should be the main flag. Maybe add a second low count flag for each team or a central flag to the map. That's enough for a good gameplay. Seven flags in one map isn't fun.
Add "angle" "#" to the player spawns that a player doesn't look in front of a wall after spawning. Replace the # with a value, e.g. 180 for the opposite viewing direction. You could also distribute the player spawns a bit more that players can't lining or spawn killing them. Try to avoid player spawns in one line.
Use clip brushes for your ladders. Create a new brush with the CLIP texture, press "s" to open the surface properties window, check the option "ladder" and click "Apply Brush". Make the effect with these clip brushes and add the ladder brushes (e.g. with the wood texture) just for visibility.
There're some places where the textures are more dark. Looks like two or more brushes overlaps there. You need to avoid overlapping brushes to fix that. A clean brush work is one of the most important things of mapping. It also helps a lot to align stuff or do easy changes. The next point should help you to avoid overlapping brushes.
Use the 32 unit grid or the 16 unit grid for more than 90% of your map. It's a lot easier to align stuff this way. Use grids with less units only for map details.
You can also scale down the textures for small boxes in the bigger grid to align them well. Just create a brush with 32x32x32 units, press "s" to open the surface properties window, set SX 0.5 and SY 0.5 and click "Apply Brush". For the barrels you need to choose an other top/bottom texture. Select the correct top/bottom texture in the texture window, press CTRL+SHIFT and right click on the faces in the 3D view to change the texture. After you've created and aligned your boxes and barrels, you can lock the textures with ALT+L. Now you can move or duplicate them without destroying the alignment.
I guess that's all for now.
Beta 3 is online @ [OTB] Beta!