I tried out both of the test builds I found in this thread; first and foremost, this has the makings of an awesome game!
For what it's worth, I had the same trouble as these guys:
I'm having trouble gauging the distance between my ship and the obstacles.
Big, big thing for me - As objects (walls, enemies) come closer to the ship/player/screen they need to increase transparency.
To be honest, along with the walls I also find that the ship itself gets in the way of my view a lot. It helps to stick right down the bottom or right up the top of the screen, but when it's necessary to be in the middle of the screen I can't see where I'm going at all!
Was it my imagination, or were the ships in the inside test with the fans harder to hit than the ones in the forest and the desert? I don't know if they were just flying further away, but I had much more trouble taking them out.