Now, I'm not a kernel puritan, my machine at home is using proprietry nvidia drivers but I understand that by doing so, I may have compromised the stability of my kernel. That said, it has never crashed or locked up, even under very heavy load.
That is new to me: why would open-source drivers be more stable than closed source ones ?
I mean: they may or may not be better... but what would make them better everytime.
Look: if I decide to develop a driver, releasing the sources won't make it any better...