I just hate how pathetically easy DF is. You can reach 90% of your maximum fighting ability in about a week, if you don't spend any real-world money. Perhaps three weeks if it's your first character.
Of course, that last 10% is hard as hell to get, unless you simply buy it. But that's just icing on the cake.
In short, I want:
1. More difficulty
2. Unable to buy infinite power through the cash shop
3. More variety (Soon to be implemented, hopefully)