Alright, so three somewhat related suggestions here. These ideas mostly come from me having played Rollercoaster Tycoon and thinking that some of its menus could apply to dwarf fortress and be a real help.
First, it would be nice if either in the units list, or in a new menu somewhere (maybe status screen?) there was more information on each dwarf, such as happiness rating, current status, and gender available so that you could see it all on one page and wouldn't need to go into each dwarf's page individually to check; similar to the current unit list's functionality of showing each dwarf's current job.
Secondly, not sure if this is possible or not, a menu that groups dwarves with the same (or similar) jobs together, so you can see how many dwarves are eating / sleeping / idle / canceling job: too injured, without having to count them yourself in the unit list. Also, by selecting one of these groups, you could see which dwarves specifically are in that group.
Thirdly, I think it would be nice to have on the main play screen (perhaps next to the idle dwarves count) some kind of indicator of the average happiness of your dwarves.
If you haven't played rollercoaster tycoon or are having trouble understanding what I'm suggesting, I can post some screenshots of RCT as examples.
Just my ideas of how to help improve the quality of daily dwarven life.