*** SPOILERS: This post contains Arx Fatalis spoilers! ***
tinyE: I just hooked up that mod; have you tried it yet? I honestly can't find that big of a difference though there are more setup options which is always nice.
I haven't yet. I looked through the bugfixes and changelogs for liberatis, and couldn't find any [clearly] related to the problems I had. That said, Liberatis looks useful for a sharper and smoother appearance. I'd use it.
It has been years, but I remember a machine on the lower levels that processed ore or something similar. It had a hole in the front in which I'd deposit the ore. Nothing would happen. (I'd lose the ore, though.) I reloaded and tried lots of times. Then I looked carefully around the machine and it turns out the ore was passing through the machine and resting on the floor in the small gap between machine and wall, where I couldn't reach it. After many reloads (and walkthrough confirmation) I finally found a drop region on the machine (not the hole) that would cause it to work. This experience was typical of the lower levels. It was as if nothing had been tested at all.
Then there was the flippin' unkillable beast. I figured out what to do: Find some bait (some piece of a dwarf, I think), place it under some crushing machine, and then operate the machine while the creature ate the bait. Many, many, many times the creature would flicker, shift, and disappear when caught by the machine. When I returned downstairs, the creature would reappear elsewhere and kill me. Other times, I would get to the machine and find that I had no bait. It took me ages to figure out, but the creature was eating the bait from my inventory as I crossed a catwalk well above the creature. It made no sense whatsoever. I figure there must have been some misbehaving proximity calculation in the code (if valid range then creature eats bait, etc) which applied even if the item was in my inventory, and I was well out of range. (edit: It now occurs to me that the calculation probably ignored height.) Finally, I was able to properly crush the beast in the machine, resulting in the beast's corpse lying on its side on the floor. I go downstairs, and bam, the creature appears in my lap, alive and well, and nowhere near his crushed corpse.
These and numerous other troubles with the obviously unfinished and apparently untested lower levels resulted in hours of bullshit. If they are problems with the original engine, then Liberatis may have cured them without explicit mention in the changelog. I'd prefer not to risk the game again until I know for sure, as this was a Gothic IV Arcania level of disappointment I don't care to relive.
*** SPOILERS: This post contains Arx Fatalis spoilers! ***