Caveat: I have never been certified for anything, and am speaking mostly as a person who has hired system administrators, but I definitely am one myself.

If you're interested in getting a Unix certification, I'd suggest getting certifications from the Unix vendor. That is, get a Solaris certification from Sun, etc. Obviously, this is impossible for Linux and BSDs (except for Red Hat).

Specifically, Sun offers two system administration certifications, Sun Certified System Administrator (SCSA) and Sun Certified Network Administrator (SCNA), which could be handy in Solaris environments. SCO has three certifications (that I'm not familiar with).

I'm not that familiar with Sair, although I've heard of them. To be honest, most of the reason I'd be interested in getting a certification would be to increase the likelihood of getting a new job, not for education, and the only way that it's going to help is if your employer is familiar with the accreditor. I don't know if Sair is going to help you out there, or any other third-party certification.