In my experience it does add flavor, but the flavor is more subtle. If you're looking for forward hop flavor you may want to augment with a flavor addition. You're not going to get any aroma from it.
I did an all FWH ESB and while it was good, I wouldn't do it again. I want more hops, both in terms of bitterness (or the perception thereof) and flavor, than what FWH provide all on their lonesome.