Got mine off ebay for a fiver! Comes with double sided sticky tape to the exact size of the fin, such an easy job - 4 months later and its still holding on tight! I think it looks sweet as!
Almost got the RNS-e but opted for the pioneer appradio2 which suited the features I wanted better (easier to fit aftermarket sound system/plus saves me drilling my roof etc) so didn't need to get the OEM sharkfin. I would say to 99.9% of people mine looks OEM, and for a fiver I can't really complain!