Yup, a bit too dark. But overall a good map. Item placement is very good. People camping on the rocket launcher can only cover the main route and are vulnerable from the back entrance. The sniper points are also well done, snipers can see where the main action takes place, but can't see the two sub-routes.
Middle area tends to crap out a bit.
Could just be my settings. All in all, worth playing and putting in the rotation for a while. It's worth a download though. I thought Chasm was a good solid CTF map. My only gripes with it are the darkness factor in some places, and I had a bit of slowdown on my 64mb ram machine.