At risk of whoring my self here, but what do you think of this one? *clicky*
Minimalistic at first, almost to the point of being bland, but I like the way it picks up about a third of the way through. You experiment with a couple of really great melodies there, but the way the first half of it progresses, I feel like it could be a much longer track.
Overall I'd say you've got a great foundation. Now build a house and lengthen it a bit.