I was looking at your tree image (Reply # 166) for minutes and I had no idea which nasty mistakes you were talking about.
Now that you've mentioned it, I see what you mean. Sometimes some mistakes may be barely noticeable, but I know, as the creator it's impossible to say, I'll leave it like that, because nobody will notice it.
In one of my images I saw, that, after a long render had finished, all the opacity maps for the trees' leaves were inverted. It was again barely noticeable from a distance, but I had to render it again.