ive got the genuine BMW ones on my 650 (mine has not layed itself down yet but ive had a couple of close ones)
they seem good value for money to me considering they have the BMW tag on them, look good next to the engine (same colour) easy to fit and dont seem to cause any extra vibration.
HOWEVER!!!! if you've got the low set version 650, dont try to go down or up kerbs, or else you scrape them
sending this on holiday in cornwall ... how sad is that???
hope this helps