I want to say that I feel that DF is the greatest computer game ever, and one of the greatest things ever.
My current gripes with the game, that often make me tired of playing it and put it aside for a while (ignoring graphics, difficulty level, obvious bugs, and other eternal issues):
1. Except for fps rate (an eternal issue). The game is just too unwieldy, and it really sucks that there is very little I can do about it. It makes playing later-stage fortresses really painful.
2. It can often be a drag assigning certain workshop jobs. The one that comes to mind is the jeweler's workshop. There should be a generic "cut a rough gem" job and a generic "encrust x with a cut gem" job. I find it to be a major chore to have to go to my stocks screen, write down how much of each gem I have, and then translate it into work assignments. I am equally frustrated with other jobs, but for different reasons, of course. The main reason being that I don't initially know how much of a resource a certain product requires. Some sort of Stocks - Work Manager coordination would be primo. This could be considered nitpicking, but it does take up a lot of my time.
3. Fluids. I find that water behaves more like a gel or goop than a liquid. This is an issue where the loss of immersion in the experience due to dealing with weird game mechanics is frustrating enough to overbalance the notion that I need to just adapt and move on.
4. Pathfinding / Dwarven stupidity. I'd like the guys to be a little smarter, a little snappier when I make decisions. It seems like a drain to have to build and then suspend building walls behind the walls I actually want to build so my masons don't trap themselves.
Of course, none of these problems have been bad enough to actually turn me off, but they stand out as major points of criticism.
Keep up the good work!