One of my past mods, Horrorshow, had a similiar feel. One player was a chainsaw-wielding maniac who chased you through a dark mansion filled with scary sounds. I still get emails that this was the only game that ever scared people. In Gloom, the fear comes from being in a dark place and not being able to see what's attacking you. The fact that the spiders can cling to the ceiling and drop down behind you leads to a certain sense of paranoia at times.
Gloom seems to be completely stable now.
There are some little annoyances, but for the most part the beta is extremely balanced and servers should be stable. Additionally, we will have a lot more levels in the full release. Right now we only have two, but the full will probably have between 4 and 6. I seem to recall that Gloom was originally being designed as a complete TC with a single-player aspect. Gloom changed from a single player TC to a multiplayer project for a few reasons.