Personally the ASCII graphics were part of what drew me to the game in the first place. A lot of games focus too much on graphics and not enough on gameplay these days. Other games I've played with ACSII graphics have had really deep gameplay(mostly roguelikes, but a few others), so I've sort of come to expect ACSII = Good Gameplay.
As a new player the biggest problem is an excess of micromanagement. It's fun at first because you can control every aspect of your fortress to make it exactly how you want, but after a while it just gets tiring. I'm sure some enjoy it still, but I for one would like to see more macromanagement to streamline everything and make it easier. Some things in particular I can name:
1) Cutting Trees/Gathering Plants. As it stands, you have to designate certain plants for this. When your harvesters run out of designated plants/trees to gather, they stop working. On countless occasions I have gotten so involved with other projects I will forget all about woodcutting until I get the message "can not construct bin: no wood:, which grinds any wood-related industries to a halt, including glass and metal. It would be nice to tell your dwarves to just go chop wood, and they would chop it from anywhere they can find.
2) Quantitative Stockpiles. In DF2 I seem to have a problem with either having too much or not enough. Lets take the wood example again. I want to keep my workers supplied with wood, but I don't want him cutting wood when I have more then enough already and my cutter could be doing something else(like hunting). It would be much easier if you could tell him to "keep this stockpile at 40-80% full". Say the stockpile is 30 squares. When there is less than 12 wood in the stockpile, he will go cut wood. When it reaches 28 wood, he will stop cutting and go do something else. This could eb used for everything; stone, food, booze, metals, etc.
3) Too much, too soon. One problem I had at the start was immigrant floods, though I suppose this could happen with other things as well. I would spend a year or two with my basic 7 dwarves, getting everything going, then all of a sudden I end up with 40 and no idea what to do with them all. It would be nice if you could place limits on immigration from within the game, say getting 2-4 at a time up until a max