I liked the feel of the game and the design of the planets, the exploration idea is good but it could have used more sense of direction and velocity while flying out there, a paralax as others have suggested and either a mini-map or radar of some sort (You did go half-way into the radar idea with the proximity arrow, that was nice).
As I said, great exploration concept, however I would have loved the actual exploration to be less punishing, the fact that you have the planets appearing randomly in the map every new playthrough counters the sense of discovery you earned on your past life, that said I did like the randomness, all I am saying is the 2 concepts between continuity and randomness kinda clash.