Davion's UI is looking pretty DOS. It's cool, really, though it'd be nice to allow UI mods (like engraved stone panes and whatnot, to replace the standard ship colored boxes). The top menu bar is a pretty nice touch.
Personally, though, I'd be happy with being able to click everywhere. Click Designations, then Mine, then click and click again (or drag, though I dunno why) and you're done. Beats wearing down my directional buttons. And, of course, the keyboard shortcuts should be preserved if possible.
And the list of things that would be nice, but that could by all means be lived without...
Isometric veiw. See the cliffs! Of course, you'd still need to toggle z-levels, but CLIFFS! WATCH YOUR VICTIMS PLUNGE INTO THE MAGMA BELOW! Without needing to swap to look down, if the hole's wide. Up maybe.
Tabbed announcement display. Job Cancel dedicated tab is blinking. Again. Always ignore it during a fight. Warnings and Alerts tag says someone's just entered a fey mood, though.
More menu tabs. Unit menu categories being toggle-enabled. I could care less about their jobs right now, how many are close to tantruming, and how can I read it without clicking endlessly? Columns, of course!
Selections and mild order-giving via the unit window. The right click function may be problematic in the main view, but it'll open a nice labor-disable window, or draft without the military screen. Maybe integrate the two as different views. Quickly, Depressed Hammers of Tallow! Join your comrades in the Happy Fun Sauna House!
Mouse scrolling. Or something to keep the 10-tile clunk down.
Oh, and coustom sound sets, I suppose. I wouldn't use it, but it'd be fun to see the twenty different sound files people made to represent a mining pick hitting stone.