When OS X was released, this claim to fame was more exciting than it is today. Nowadays, Linux / GNU dominates what it means to be a mainstream Unix-like operating system.

The extent to which other *nixen deviate from this determines how much of an uphill battle one will face. And I say this as a lover of OpenBSD, and someone who wishes Linux weren't such a dominating de facto standard.

But the Open Group--I can't think of one reason why UNIX certification has mattered for a good number of years now.