As I was playing, I took a screenshot every time I saw something wrong, so that I could post it in this thread.
By the end, I'd taken a total of thirty screenshots.
So. Because it's a bit of a pain to de-tiff/crop/upload so many images, I'll just summarize the most critical ones.
1) The intelligence rooms feel
really weird. Why would a room have those open top windows built in that way? (Especially with those textures?) Why on earth would there be a door opening in the ceiling?
2) Similarly, right outside the spawn room - why would there be a door opening into a hallway from above like that? It just felt
very strange. (Also, it didn't quite work right. You had to jump to get through it, even though there was a ramp leading up to it.)
3) The intelligence rooms badly need nobuilding. At least twice, the enemy team set up sentries in our intel room - sometimes literally on top of the intelligence! - which were a pain to wipe out. (The ones on the opposite side of the room from the intelligence weren't so bad, because you could grenadespam through the windows to take them out - possibly part of the idea behind their placement - but the way the main entrance door slides open (why
does it slide sideways, instead of up, like most doors?) makes it very hard to take out sentries closer to the intel.
4) On the balconies, there's a fairly large room that contains a great deal of... nothing. Why does it exist? What purpose does it serve? It felt like it was crying out for, at the very least, a health and/or ammo pickup...
(Similarly, in the upstairs part of the respawn areas, there's a rather large room containing... nothing. A resupply cabinet would be nice, at the very least.)
5) The tiny little doors leading to the underground tunnels are very odd. Why do they need
little ramps leading up and down to them? They just seemed superfluous. (Also, red's drop-down door (from the respawn to the tunnels) was too small - you had to crouch to fit through it.)
6) More minor things: use of TF2 textures (especially in red's base), a couple of z-fighting problems (textures on top of each-other) - the roof-doors leading to the intel were the worst for this - a few misaligned brushes (gaps in the walls) - the support-struts on the outside bunker-things (sheds?) were solid, and could be climbed on (even though they looked like textures) - the roof-doors leading to the intel are triggered incorrectly, so that if two people try to enter, the door will close after the first and leave the second locked out....
TL;DR VERSION
TL;DR ALERT
The base needs
massive simplification. Cut it down to a third of its current size. Remove most of the moving parts and clutter, like the door-ramps in the tunnels.
Then work on the details.