I did some timings:
14s - main path through tunnels
21s - high path, dropping down to the flag
25s - low tunnel, short ladder
28s - low tunnel, long pole ladder
As you can see, it takes twice as long to take the low path. If you ended up on this path, somebody could do an entire flag run through the main path in the same time it took just to get to theirs. You need to balance that out a bit more or else everybody will always take 1 path. My suggestion would be this:
Split the map up into 2 paths. One that goes to the low tunnel (basically what you have currently), and another that wraps around (maybe you could make use of the ramp to the spyder) and goes to the high tunnel path. I've attached a really crappy sketch to point out what I mean. Hope you can follow it (man, I hate ball mice).
Also, you need to work on making the walls look more natural. Throwing in a couple extra brushes and using clipping planes at various angles can do wonders for making the level a little more convincing. Take a look at
bombsaway, for example.
Also, I'd suggest using sun lighting instead of light fixtures. It's a day time sky, and in some areas, I can see the sun, but it's pitch black (second shot).
As usual, the map is up on the beta server for play testing.
