I saw this post linked from the Kickstarter page. I really like mazex's #6 - Final cut with background for the names and flags on the same row as the gun.
The names (and the flags to a degree) really help me connect with the soldiers. I like the font and background for the name - it makes it easy to read. And I like separating out the time units to make it more of the focus.
Sheepy's UI mockup is also good. My favorite parts were these three -
Outline move area, move + shot area (before turning), and vision cone.
When selecting move location, show line to all enemies, and who can be shot from that location (after turning), and whether each can see you (red eye icon in the mockup, above the left alien). Default to move + fire instead of ignore move and fire.
When hovering over target, see accuracy of all modes. See hovered target's TU and HP but without numbers.
All of those would be very useful for me.