Rock solid so far. I mean, it does let the screen rotate a tiny bit if i force it to stay midway between closed and open, but it snaps quite strongly towards each extreme and once there i can hardly tell it is supposed to move at all, but other than the magnets (or is it some complex/clever springs system?) i fell no resistance to closing nor oppening.

I imagine i might notice some difference if i feel the slide in a N900 fresh out of the box, but without having such a comparison it feels pretty much like it never changed from the time i got it to now.