I accidentally picked up a bag of rw feathers a while back. I was out of lw, so I fletched a couple arrows with them. My jig is left helical, so they were on backwards, upside-down, whatever. They looked a little odd, but they flew just fine. Supposedly, you can't get a right wing feather to twist left...well, that's not true. The only thing I did notice was that the fletching didn't seem to stand up as far. Maybe the wrong twist makes the fibers lay down a bit.
As far as flight, no discernable difference.