Well this is just my opinion, but the player felt weightless to me. I understand that part of the game is a jetpack, but he just seemed to float, like the jetpack didn't provide much thrust up and prevented me from falling down quickly. If you increased gravity for the player by a bunch and let the jetpack provide more of a boost it might make the player feel a little more present.
Not that I want to push my own stuff, but I put together a set of control schemes just to play around with them. http://codingadventure.net/index.php/projects/control-scheme-test The one in the lower right is a jetpack. The acceleration is fast in both the + and - Y direction, so it feels like the jetpack is really pushing the player up and gravity really feels like it is pulling down.
Again, this is all my opinion, and if it controls exactly the way you like it then ignore me :)