I have a small streak also that I just whipe off on occassion.

If the cause is REALLY grease on these little "brushes" that guide the window, couldn't you just take apart the door and degrease the brush yourself?! That way you know it doesn't come back? It's not something you should have to do on a car of this stature, but obviously Nissan isn't the best at fixing this issue...

 

ahh... so now i might have to retint the window?? =/

 

i'm getting both driver's side and passenger's side windows for free because they have actual scratches on them.. they're going to be tinted too (cuz mine are tinted right now)