This is a nice shot overall. Has anyone told you yet that your horizon is tilted? :P I think the strong leading lines of the water channel and rocks take the viewer off-center some, meaning that this doesn't feel that centered. A polarizer may have helped to control that sky a little.
Now that I look a bit closer I notice some strong haloing around the tree and the upper rocks, yet the photo doesn't seem oversharpened. Been playing around with HDR/Tonemapping a little perhaps? :D
This is a beautiful photograph - not sure that it really could be called a centered composition (indeed it seems to follow the rule of thirds), but it is so lovely that I am marking it high. Had it been a true 'centered composition' it would have got a 10 from me - but there again it wouldn't have been the same photograph - hmmm...
Oh, and certainly adding it to my favourites.