Hey Lorant,
I really like the comp although I might have preferred a bit more DOF so the dunes were a bit more in focus. You may want to take a slective levels adjustment from the trees up......to tweak the tones a bit more.....but comp wise you nailed it!
agree with Roman on need of more DOF. I am somewhat fine with the dunes but a sharper treeline would have made a big difference. A round of USM there might be helpful.
Yes to 'nailed the composition'. the BW conversion looks nice as well.