I'm not sure the vibrate rattle will be "fixed" any time soon, it might be related to a hardware design issue or supplier issue, in which case we won't see something solid for a while, and you'll have to rely on getting "lucky" devices that magically don't have the rattle. I've gotten used to it at this point; the only thing I'm worried about is whether or not the rattle can cause further loosening or degradation of the parts involved in the rattle, or any parts that may be getting abused physically when the phone vibrates.
If I can be sure the rattle is purely a noise, and not hardware loosening or degrading, then I can live with it. However, I don't know what it would take for me to have confidence that it's true. I'm not sure a statement from M$ or Nokia would do it, as I've had the wool pulled over my eyes by manufacturers before (*cough* Crapple *cough* Samsuck *cough*).