In additional to jitspoe's feedback.
Make the name of the mapfile all lowercase.
You need to rotate the viewing direction of the red player spawns (mirrored "angle" "#").
It's right, that lots of stuff looks slightly misaligned. As already mentioned, using the 32 unit grid will help you a lot to avoid this (brushwork and alignment).
The jump pads are a bit powerless sometimes. Would be cool if they would work well all the time.
In my opinion the high walls are a bit unfavorable for a DM map. Maybe you can try to avoid them for some of your next maps.
Some screenshots...boxes, barrels, etc. are just examples. I don't want to make a screenshot of each box or barrel
Red: This kind of ramp is something for advanced mappers and doesn't look good how it's done at the moment. The clipping planes will help you to make it properly. But I'd prefer an easier ramp solution here.
Red: Same...
Red: All barrels are slightly misaligned. You need to move the textures down for only 1 unit. The top and bottom textures seem to be ok. (the 32 unit grid would avoid that)
Red: Same with almost all boxes. You need to move the textures down for only 1 unit. Also the small box seems the be a bit to big. (the 32 unit grid would avoid that; too)
Red: Move this textures a bit that you don't split the tiles.
Yellow: Move this face a few units, too.
Yellow: Rotate this face.
Red: Wrong texture.
Green: The textures doesn't fit.
Blue: There's a small edge that can block you. (the 32 unit grid would avoid that; too)
Green: There's a small edge, too. Because of that there're some troubles with the water brush. You really need to make sure, not to create those edges. (the 32 unit grid would avoid that; too)
Red: Some more unclean brushwork. (the 32 unit grid would avoid that; too)
Red: Move the wall textures a little bit like it's done on the right side (green marks).
Red: I'm not sure what you've done here. I guess it's an overlapping brush you can delete. But might be a lighting issue as well.
Renamed the map to area52_b1. It's online @ [OTB] Beta!