I've only used green wood (other than fruit) a few times and was not very pleased. More smoke and filled my cooker with soot. The meat tasted fine, not much difference than seasoned wood maybe a touch bit of bitter. It was just the smell and the soot. I may try it again but it will only be after my seasoned supply runs out.
I do however use green fruit woods (peach and apple) regular and have had good luck. I actually prefer the flavor over the seasoned fruits. A lot of people say that they can't tell the difference so maybe it's just me knowing that it's green.