Not bad
There were obstacles you just can't avoid (since the jump takes was uncontroled) so you would go game over sooner or later (depends on how the obstacles are placed). Perhaps this is meant to happen. If you would be able to controle the length of your jump (with arrow keys or something) it would be easier. Than adding some levels and power ups could really make this game more interesting.
But as a simple game, this game is okay and pretty well done.