Is this game the medieval fantasy equivalent of Deus Ex?
No. I haven't played Deus Ex, but I have heard that its main draw is that there are multiple ways to complete quests. In Arx, the only way to really get anywhere is to sneak around and avoid enemies, or hit them over the head with your weapon. I don't recall any dialog choices with the NPCs in Arx either.
A more accurate comparison is "a watered-down Gothic 1" or "watered-down Morrowind." Some people absolutely rave about this game, but objectively (as much as I can, I'm only human) I find that its contemporaries offer superior gameplay and RPG options.
That said, I think the most impressive thing was the crafting (cooking/baking) system, I enjoyed that part the most. Still, it turned out to be a bit limited in the long run.