ken,
you took the 3 photos on the left and made the 4th, larger image from those? ok, i'm impressed! i'm not even going to to go into nit picking mode on this one. i cant find a seam. i cant find anything wrong with the lighting and shadows. i dont see any perspective distortion that you sometimes get with a skew or perspective alteration. about the best i could do to be on the super-critical side would be to say add a bit more blue to the sky for contrast, but even that seems a bit silly in light of the excellent work you did of compositing these three images together like you did. if i were to run across your final image without you having first said you made it from the other three, i would have never suspected.
and yes, i'd like to know what you used also. frankly, you dont need a critique, you need to write a tutorial
Craig