At the start I thought it was too plain, but the music really helps the game.
I think I get the ending - you guys should put it into context as well, if you think the guy has nowhere else to go now anyway (you explored everything there is and found no one).
I don't fully understand what one of the worlds is about though (the red teleporter one, it was the last one I went to). The free hanging rocks world was the best one for me (also the shortest though as I'm decent enough to make the jumps mostly at first try) - unfortunately I think I missed the point of that one as I didn't see enough of it to get it either.
Does anyone have screenshots of all 4 worlds? I get the feeling that would help understand the ending even better.
Ivo.