Bugs:
None noticed.
General Feedback:
Pluses:
1. I like how the stealth gameplay is entirely optional. It's like getting two games in one. (that said, vanilla quake weapons...again? *sighs* Then again, some people seem to prefer things that way...)
2. Visuals are amazing, love the walls that turn transparent in stealth mode.
3. AI pathfinding seems to be working well, I liked how the start map fiend knows how to use the button to get out and kill you. >=D
4. Map alterations depending on route chosen?! Awesome.
Minuses:
1. Start map can be a little confusing because you need to shoot some buttons to get into the vault. I didn't see them right away and ended up wandering around the map not knowing what to do. Also, some secrets / areas seemed...not immediately accessable. Maybe they become accessable later?
I'll update some more once I finish with it.
EDIT:
Finished it, no bugs to report. AI navigation appeared flawless. Also, I now belatedly noticed the highly id1 inspired map design.

All that said, stealth really isn't my thing...suffered through the first map in stealth mode, stuck with it through start map redux, ditched it for "Castle of Shadows", had a lot more fun playing oldskool-style. (guess I'm just the "kick ass and chew bubblegum" kinda guy...)
Excellent atmosphere, the floating book thingies were cool too.
All in all, I give it 9/10 score.