So I broke down and bought the ACKS books. I don't have the actual physical copies of the book yet, and I really haven't studied the player's book just yet. I've been reading the core book PDF to convert my old character into an NPC lord, so most of the things I notice have been relating to dwarves. But I thought I would give my thoughts on a few things.
Poison: In ACKS, most of the poisons aren't instantly fatal with a failed saving throw. Most of them you have a handful of turns in order to act before you finally keel over and die. Plus there's some very clear rules on harvesting poisons from various monsters and plants, and there are only a couple of harvested/extracted poisons that are fatal. Most poisons are much weaker when used on weapons.
Energy Drain: I've never liked how energy drain worked in D&D, and it works the same way in ACKS. The only way to restore lost levels is with ritual magic.
Divine Magic: Casters of divine magic cannot cast any spells at 1st level, just like the old D&D. That would really bring the suckage for running a party of starting characters.
Infravision: Dwarves, elves, orcs, and halflings do not have infravision in ACKS. Gnomes do, goblins do, and kobolds do. I feel strongly that dwarves and orcs, at the least, should have infravision of some strength.
Magical spell research and magic item creation: The more money you have, the easier it is to get done. I can see the players hiring several carts just to bring bits and pieces of monsters back to turn into magic items. I really like the spellcasters being able to use an example of a magic item in order to not have to learn a new recipe.
9th level tidbits: The game does have a nifty set-up for followers once you establish your stronghold, but I find it a bit lacking. The thieves, assassins and elf nightblades get 2D6 1st level followers and the mages get D6 1st-3rd level apprentice mages (and 2D6 normal men who want to become mages). The rest of the human classes get various dice times ten 0 level followers, and D6 1st-3rd level of whatever the character's class is. Dwarf vaultguards, dwarf craft priests, and elven spellsword both get the same followers (3D6x10) 1st level NPCs (quoted from the book directly). It's a little hazy as to whether the dwarf classes and spellsword get actual 1st level vaultguard, craft priests, and spellswords, or whether they're just the regular NPCs like from the monster section of the book (which is most likely). They really should have students like every other class. I've always felt that each class should get a chance for unusual followers of some sort (something like the rangers got in 1e AD&D). A giant wanting to serve a high level fighter with an awesome reputation, a young dragon wanting to learning from a wizard, or even some other type of monster that, for some odd reason, takes a liking to the character.
I like the special rules for chaotic domains.
Dwarf characters and elf spellswords have VERY restrictive rules for building their strongholds. They can freely build in wilderness areas. But dwarves cannot build in civilized or border realms belonging to humans or elves, only in dwarf realms. Elves have the same thing, but they can't build in anything belonging to humans or dwarves. A dwarf's stronghold has to be mostly underground. Only 25% of the total GP value of the stronghold is allowed to be aboveground, and must be made of earth or stone. An elf's stronghold has to be built "in harmony with nature", which basically means that no matter the material is actually used to build their buildings, it costs as much as stone. There is another nifty effect with the elf's stronghold. Because of their harmony with nature, all the animals living within 3 miles of the elf's stronghold are friendly to the elves. The elves can communicate with the animals as per the spell speak with animals, using them to deliver short messages, warn of strangers approaching, etc. Any spies and thieves within the territory suffer penalties to their hijinks.
Dragons: Oh my lord. Dragons in ACKS are frickin scary. There are rules so basically you can make each one unique, and the older they are the more awesome they can become. No more AD&D dragons with claw damage equal to a shortsword.
Most of my complaints are minor nitpicking, but overall I really like what I'm seeing here.