Not sure if anyone is still following the original post, but I am a new player who has been turned off. I've logged in countless hours on roguelikes and even won at them once or twice, so I'm not someone who can't handle ASCII, steep learning curves, or death. I played DF extensively for about 2 weeks, but I'm just done with it at this point.
I put up with a lot from DF, because I am so enamored of the idea that I am a part of an organic, evolving world and I feel that I am having an influence on history as a mortal hero. That's awesome. I also really liked the detailed combat/wound mechanics (outside of the imbalances which I'll cover below).
The learning curve is steep mostly because of the interface... it could not be less intuitive. The first time I played, it took me 15 minutes to figure out how to get my dwarves to dig a bloody hole in the ground. Even learning basic tasks in DF was too much to handle. It wasn't easy even with the wiki. After 2 attempts, I gave up on Fortress Mode at first, and switched to Adventurer mode in the hopes that it would be more similar to what I'm used to.
Adventurer mode is great, but unbalanced as hell. It doesn't matter how well developed my character is... any stooge with a bow is capable of taking me out. Starting characters are also too powerful in relation to developed characters. What I mean is, since there are no stores except for human (which only sell shitty iron items in any event), you can't upgrade your equipment to any significant extent unless you built it yourself with an earlier fortress game. Also, with only an hours play time, my characters are able to defeat legendary creatures like giants, who were around since the beginning of time and might have 15 kills to their credit. That shouldn't happen. The top melee creatures should be much tougher to beat, and a typical archer should not be so difficult. I would weaken bows a little, lower the starting character talents a bit, and have more powerful weapons/items readily available in stores.
Oh, and blundering around towns looking for stuff is excruciating. Make the towns smaller!
Anyway, after learning the mechanics of adventuring I tried fortress mode again and did quite well. I then found that the game is too easy once you know how to play. Once my fortress had external defensive walls, fortifications, traps, and a population of about 50 dwarves, I never felt like I was in any danger at all from external threats.
Attackers should be more numerous and more direct. The vast majority of enemy encounters were thieves and ambushers... I'd have liked more sieges with higher numbers of troops. I don't agree with the previously mentioned ideas of weakening traps or adding wall destroyers unless the dwarven AI is also improved, because traps/walls are a known quantity and you can never be sure what your military is going to give you. Do your archers have 25 bolts or only 1? Are your melee troops where they're supposed to be?
Once my fortress population reached a certain point, all of the micromanagement bored me to tears. The last 6-7 hours of my fortress time were spent killing off hammerers (who by the way, killed more of my dwarves than the goblins did), building 850,000 barrels, getting annoyed at the whole concept of nobles, and building new bedrooms to hold migrants. I'd have liked the chance to send an assault force against the goblin or kobold civ. Something.
So after about 5 years I abandoned the fortress and started playing another adventurer. An hour later, I got the Nemesis Unit Load fail error. That was the deal breaker for me. For a game which offers as much as DF, I can learn complicated rules and a weird interface. I can tolerate imbalance. I can work around annoying things like nobles (I had planned to reduce my max pop to 50), but I can't deal with game destroying bugs. In a game as immersive as this, where a main part of play is the evolution of your region, nothing sucks the joy out of you like having everything suddenly get destroyed by a bug. As soon as I read that nothing could be done to restore my game and that the bug was not that uncommon, I erased DF from my machine and likely won't touch it again for several years - if I ever come back at all. Whatever other changes get made to DF, bugs like that have got to be eradicated. Roguelikes have steep learning curves and ASCII graphics, too... but all of the ones I've played are reliable.
I'd make bug resolutions the top priority, then fix the interface, then add the ability to perform routine tasks, (like cooking and brewing) automatically, and finally work on the dwarven AI. Most people will put in the necessary work to overcome anything else, because the game concept is one of the best I've ever seen.
Just my two cents... well, more like 200 cents with the length of this post :-/