Just going to list things as I noticed them.
The end turn button took me five minutes to find. I'm sure you have a big button on the way, but figured I'd mention it.
The middle button being the panning button feels a bit out of place. The option or default to use the left mouse button is more intuitive, methinks. Especially if you won't be dragging the left mouse button at any time. See Endless Legend's/Civ V's default.
Having to select the "Move" button to move fleets is not ideal. I should be able to right click my destination and it move without having to first select move.
I was intercepted by pirates and they destroyed my unarmed fleet, but the fleet survived on the strategy map and I was able to continue moving them. THEY WILL NEVER GET ME!
Combat feels a little clunky. Very pretty, but clunky. I'll play more in order to better specify why feels clunky. Might be the fact that again, I have to select commands. Would be better to see a target reticule when I mouse over an enemy, movement icon when my mouse hovers over empty space, etc. Less clicking = best.
Overall, the game feels very exciting. The graphics and art are top notch and this early beta build feels solid. You guys are doing well.
I'll keep adding to this thread as I play more and invite others to do the same