It was me, who said that people liked pixeling trees (i think)
Anyway, about the piece.. As Bacteriophage stated it's a little bland. I think it is mainly because as said before the straight-ness of the tree. I also think it's because of how it's shaded. It seemed to have been shaded like every part on the left is being hit by light and the opposite for the right. This is true, to an extent. I personally think you should make it have more elaborate forms or dents which would make the tree more natural and also change how the lightsource effects it.
I might be talking nonsence, as i'm no Tree expert