First of all, thanks again for the promocode!
Now, here we go:
Yes, it works perfectly fine on the Pro, no black bars or anything. The UI and non-unit graphics look really good too.
But the pixely units are ... well, too pixely. Matter of taste, I know (some folks even like this kinda stuff, I hear

) , but not my cup of tea.
This would be somewhat forgiveable (it's just about hitting my "too pixely" threshold), if
a) the rest of the graphics wouldn't look so clean and crisp, making the pixelstuff stand out even more in sharp contrast.
b) the camera wouldn't zoom in for moves/attacks, showing the pixel figures in all their "glory".
Other than that, after playing two scenarios, my first impression is that this could be a good game.
However, it clearly shows its age as things I expect are missing. Such as:
1) No "undo move", no "replay last turn", no "restart mission" options.
2) Doubletap instead of singletap to attack.
3) I had "no move confirmation" here, but just found the option to turn that on in the menu

But I didn't expect it to be there, to be honest.
4) No "next/previous unit" button(s). Not that you need them early on when you only have 4 units. But I expect that my army gets larger, and once I am past 10 units or so, I really like to have that.
5) "Guard" (basically "end turn for this unit") and "delay" (till I moved all other units) are missing as well.
On top of that, the constant camera zoom in/out when moving/attacking is extremely annoying and, much worse, made me a bit dizzy after like only 5 minutes or so (played first two missions). In addition, I settled for playing on max zoom out after under a minute, and after every move/attack I need to zoom back out again.
Then, I always see the Gamecenter icon at the top middle of the screen. Distracting, shouldn't be there.
Why does the "End Turn" confirmation button slide out to the right after you hit "end turn"? While this shouldn't be a problem on smaller devices, on something as big as the Pro it's annoying: I either need to stretch my hand or move it to reach the button after sliding out. As I have RSI, any unneeded movement/action is extra bad in my book. And I have large hands and long fingers, put next to each other vertically, they cover almost 2/3 of the screen in landscape position. For people with smaller hands I imagine this to be even more annoying.
Given the age of the game, I do not expect that you update it anymore. But I do hope that you take the above feedback into account when/if you make another one.
I'll play a bit more later, mainly to check if the getting dizzy happens again.