I played through this again, in the belief demo recordings work in GoldSource (I guess I don't have to say they didn't). I played it a little more 'thoroughly' now, and I found a couple few glitches, most of them related to monsters (npcs).
On the media group floor (I think it was JeffMod's) you can use an ai exploit on that guy who killed someone (really, what happened there) to retreat all the way back to the stairwell. A bug native to GoldSource (and appearently not fixed in spirit?) cuases the ending door to open if he touches it. Even worse is he can pass the security shield without any problem. He can't come back through since the trigger_push in there affects both players and NPCs. If you then proceed to go through, he will lock you in place kicking you indefinetily, since you instantly regain health, and you just lost your weapon.
On the floor where you have to find the power cells (Tetsuo's?), if you let the agrunt walk around for a while in the holding cell, he may eventually get stuck in a wall. This prevents him from walking to the scripted_sequence, and prevents any progress.
On Strider's floor, if you don't know about the first power locker and don't care to look for stuff like keys, you might think you can be so sneaky and just rush juuust under the sensors of the camera through the door. Of course, the camera will trigger anyway, but you will just have touched the autosave cuasing the death loop mentioned earlier.
That's all I found on this playthrough. I will come back later if I find any more bugs and glitches. I'm also planning on making a video walkthrough of this, hence the mentioning of the demo recoring tools at the begining of this post.