I picked it up yesterday and am enjoying it in bit size chunks. I have about 3 hours or so into it so far. The game definitely shows it's age and feels pretty clunky. The combat does not feel precise or "sharp". Walking around is a bit of a chore because the paths are pretty precise. You can not tread freely. Also exiting a "zone" or map location must be from specific points along the maps edge which can be difficult to locate at first as the mini map is pretty poor (in my opinion). The quests log can be a little vague as well. That being said...the game is pretty fun! The character creation system is quite unique, the story seems to be pretty complex and well written and the narrator is great. There is nice variety in weapons and magic use. The game dares to kind of break the mold in mechanics and I can appreciate that. For the 3 bucks I paid I am more than happy! It is worth the asking price as well.
Oh...it shares some similarities to Diablo gameplay as far as being a real time action rpg but it is no where near as fluid or fast paced as Diablo. Diablo is more of the ACTION and Heretic is more of the ROLEPLAY in terms of them both being from the same genre. Some opinions may differ however.
I agree, from the very beginning game actually favor player and suggest to explore, talk, make decision and do the quests. Characters along with main heroine feels more fleshed and alive to entertain you more if you decide to involve yourself deeper. There is unique skills and levelling system that depends what you do is what you get better. Also attunements and Dreamworld. For those who want discover whole different way to play entire game, choose Dreamform from the very beginning to roam it freely.
PS. Game features uncensored, full nude version of heroine which is not active by default but is only a matter or renaming some textures but since you start game from complete null to story, training and mechanics introduction it would look goofy to run all the time in nudist mode (although there are certain attunements for playing without armor however). ;-)