I caved in and bought the alpha.... First impressions.
This game has more or less nothing at all in common with Hexen/Heretic - do not get this game if this is what you want. However, it is not a bad game in itself.
Gameplay - you are put into a random map with connected rooms. Each floor have a portal key you need to find and a portal guardian. You wake up the guardian with the key, and need to defeat him to go to the next floor. Rinse and repeat. At the moment there are 5 floors. Most rooms are arenas with x number of minions which must be defeated to open the doors, but some are also trap rooms, special loot rooms or other combat oriented rooms. You start out with a wand, which regenerates mana, and you need to find other weapons (spells) which uses one of the other 3 mana resources which are limited (red, blue and green). So far I have not found many spells, only a frost spell (shot gun) and a fire grenade spell. Mobs drop loot when killed - XP, mana or health, which disappear after a little bit (so you can not camp...). You level up every now and then, which increases you HP and mana pools (not sure about DPS yet) and each time you level up you get a choice between 2 perk 'cards'. As you play, you will unlock more types of perk cards.
There is also a choice of characters you can unlock as you play, the beginning char is vanilla without any pros or cons. You will need to invest quite a lot of time into this game if you want to unlock all chars and perk cards. Not sure yet if there is enough variation to keep you interested for that long.
Graphically, the game somewhat reminds me a lot about the Orcs Must Die series. It has a very annoying motion blur effect, which thankfully can be turned of... The engine is descent and it runs fine on a laptop with intel HD 4000.
If I want to compare it with other games, then the closets would be Tower of Guns - without the spacial game play (Ziggurat is 'flat', all action on one plain) and the turrets. A bit like a more hectic version of Fancy Skull, maybe. Still, it is good for the current price, but it needs a little bit more content.