KS2008: When should drivers be merged?

Releasing vendor drivers wouldn't really help much, since it's pretty late by the time users get anything released by the kernel team. Getting drivers for pre-release hardware to kernel reviewers under NDA could be a big help, though, particularly if that included distro representatives who could get a package for the module through QA and ready to release simultaneously with the hardware. I wonder if big hardware vendors would be interested in the linux driver project that Greg KH runs, for the express purpose of collecting acks from reviewers (and, of course, comments, but those would presumably be uninteresting before they could be posted) in advance of the code going out to the world.