So windows is the only way to go?
Does people who have 12rigs have 12licenses to windows?

There aren't any other os that can oc?
So cudaMiner can't OC like cgminer can?
cudaminer is lacking quite a lot of features that cgminer offers. Failover, monitoring APIs, overclocking
some of this is on my TODO list.
So it is fair to say that if the failover isn't in the feature-list this nVidia can't compete with AMD