I installed the OEM crossbars on the SLT a month ago to pick up the Christmas tree. I've noticed no difference in mpg's with them installed since then. Which is good, because they're kind of a pain to take on and off. Previous vehicle had a clamp style (very easy to install and remove) with a noticeable drop of about 5 mpg's on the highway.
So now you know!
No added wind noise. However, I do drive with my stereo on. Not “trying to go deaf, loud” but I enjoy the Bose system. Could be the added white noise system blocking it out to, not exactly certain how that all works.