The main problem I have with these flaps is that, when the rear seats are folded down flat but the parcel shelf is left in place with the flaps dangling down, the studs make an infuriating rattling noise.

x2
And when it happens the firts time you need some time to find where the noise is comming from ... grrrr

Other than that I must say I don't have anything to complain about it.
I have others things to complain about (rattling noise from the dashboard, windows trembling when a bit open...)