According to what is said on their webpage, the team leader was a Hexen fan. When he was playing Doom 3 and saw Hell levels, he thought like "woah! this is a nice setting for possible Hexen ressurection project".
I tried it recently... ofcourse it is hard to make conclusions on what seems to be mid-alpha stage, but so far I can't say I liked this. In fact my reaction was like "lol wut?? WTF??"
The game setting does not have ANY similarities to original Hexen atmosphere. In fact, I think it's more similar to Hexen 2, plus something very Doom3-ish. It's hard to describe right now, just a feelings.
Authors added new monster: a jumpy imp with burning back, or something like that. Ettins look formidable and move much faster, - good thing IMHO. Also, the new addition is a possibility to block attacks by a shield, which, when successful, reflects all damage.
Anyway, problem is that the game is barely playable at the moment because of very stupid attack logic. For unknown reasons those good people made a mace work like a gun - it hits enemy only when the crosshair is EXACTLY at creature's model. I could kill all Ettins very easily, because they have large bodies and move straight, but the little demons I mentioned above did not leave me any chance (I was loosing about 15-25% health for each killed bastard, and health potions were very few).
Real surprise is AI though, because monsters are dumber than in original Hexen: they only start an attack when you come close and have zero navigation. A very strange thing, assuming mod authors work few years on this already.
EDIT: I found the mod features original hexen cheat codes (like quicken, rambo, indiana etc). So I toggled godmode and ventured futher... I better not, at least I could save a hope
. For now I find this mod simply disgusting. It does not look like Hexen at all, not even like Hexen2. It is Doom 3, with alternate weapons, enemies and level setting, no more.