It has the potential to be a rage-inducing game, that's for sure
That could just be that I'm bad at it though.
The overall controls are nice, I see now that you added a left and right propulsion (Q&E) since I last played. This is hard to explain, but at times it can get disorienting and hard to tell whether you're travelling right or left, up or down.
The graphics are really cute. The simple art really fits the gameplay. It lets you focus more on the objective than being bombarded by flashy art.
The gameplay is nice and calming, although it can be a bit aggravating if you mess up one little bit, since it's hard to recover. And expanding on what I said above, losing track of what buttons you're pushing can sometimes cause you to lose track of which direction you're travelling. (Which I guess in a way is part of the challenge of the game) The collisions of the ship can make things a bit annoying too. You think you're about to dock when wham, you explode. Especially on the levels with moving parts to dock onto. EDIT: I realize now after playing a bit more that this could have to do with how fast you're travelling, etc.
As for level progression, it can be annoying to go from a straight shot to dock (Level 1) to a moving platform that requires you to travel at more of an angle (Level 2). I'd say make each level introduce a new added challenge, don't just throw the player in. (Especially on starting levels. These are the first the player will play. You don't want them to get super frustrated without really getting far into the game.)
Conclusion of this cheap little review
Different parts of what I said above could apply towards helping improve your game or not, depending on the type of game you're going for. All-in-all though, I really enjoy this little game Great job so far.