Back to Hellfire - a nice mix between Diablo 1 and 2.
Old school multi-leveled dungeon clearing experience (explore whole level, open each box, grab all loot)
Unique skill system - gain skills by reading books from loot (two random books = 1 random book for your class)
Unique runeword system - each rune is syllable, combain them into real english words - get runewords. Same runeword works in any item as long as socket number is right. List of rws is not available, so have fun discovering.
Real use of merc. Bow merc from act 1 did a lot of good damage for my char. I can say this is probably first mod where i was fully relying on merc and was satisfied with effect (ofc dumb AI moving patters still exist, but you will learn good ways to make merc follow very fast).
Plugy works. Restat of stats works via pluggy settings, restat of skills - no need.
Grindy as hell. Stuck on some level and cannot go down ? Tough luck, rerun this level many times until you find better item/get more lvls or just luck factor.
Books drop but the RNG of getting the book you need is most of the time the real ragemeter. Want that book for barb axe mastery ? Too bad here take this leap atack book
Cain charges 100 gold to identify. ID scroll costs 72. Hmm...