*breath in*
Humans > Dwarves (thankfully it's easy to play as them, who wants a barrel-sized, bearded hero? Who would play Demon's Souls if your character was half a meter tall, huh?)
Tall spires > Elegant fortresses and gardens > Confusing mountain halls
Two-handed swords > Long swords > Short swords >> War hammers
Steel > Iron > Bronze > Magic Candy
Flax > Peahen leather >> Stupid, unrealistic spider silk
Nerve damage is brilliant and an excellent feature, and if I had to name an example of the things that keep me playing that would be one. Needs accurate nerve, artery and muscle compartment simulation.
Adding magic in the form of night creatures and necromancy to the game was a bad idea and has severely detracted from the atmosphere. In many ways, 40d > DF2010. In fact I still play it. Why couldn't you do steam power instead of magic, huh?
Adventurers should be able to randomly trip on roots and break their neck. Hunger should still kill you. Meeting strange civilizations should give you exotic illnesses that make your kidneys rot and eyes bleed.
Expand the ascii set to include Chinese Characters, so you don't have to represent everything with the same symbol.
What the game needs is more fleshing out of the anatomy, disease, job system, farming and construction, not story arcs and magic.
On the other hand if you're going to add a story, do it properly by letting players pre-define kingdoms and heroes and their relations so we can create scenarios, procedurally generated things are just stupid 90% of the time. Seriously, if I want to generate Wind Kingdom Rolante with its princess in the mountains, let me do it so it doesn't end up The Civilization of Soapberiddled in the land of Armpitsweatomens situated in the Hills of Sociolinguistics and my heroine getting named the Obscure Dimples of Lucrativeness. It was funny the first maybe 3 times, but if you want to get really immersed it gets really, really stupid. What would make this game really good would be the ability to add pre-defined scenarios a la Battle for Wesnoth.
Somebody should create an open source clone of the game to compete with Toady, like has been done for many other closed source.
Sorry.