Theres some definite vignetting going on here. I dunno whats being referenced in the dark clouds comment, but I see it - just don't know it it "distracts" (doesn't to me, rather like it - whether it was intentional or not).
#1 and #2 I feel like they are these unfinished thoughts. . .or maybe there was the excitement of seeing an awesome scene, but you blew your load too quickly. How awesome would it have been to get your friend bouncing over the hill in the second shot, flying out from the left and heading to the right.
In the first one, hes too much part of the "scenery" for me to really "care" about his placement in the picture, when I would have liked to see more of him, and his dust cloud. . .
But if you took him out of the first picture, and got rid of whatever is casting the shadow in the lower left corner - this would be a photo I stick in the "NEVER EVER DELETE" folder, and come back to often. . .