There were several OpenSolaris related comments and I'm all for using it. I've installed the 200805 release in a VirtualBox VM on my Mac as well as native on an old Dell I have. And I recently had an opportunity to get a release candidate for the next release and it is improved but I don't know that it quite has all the apps I want/need. I'm going to continue using/tracking it though and would gladly switch to it as my primary OS when it is "ready". But I don't know that I'd go out of my way to run it on a Mac and certainly wouldn't spend Apple money to buy a new machine to do so.
Related to the above, there was a comment about using Ubuntu. I've used it (or its variants like gOS and Linux Mint) both in VMs and native and feel it is still ahead of OpenSolaris as a "regular user" desktop, but similarly wouldn't buy Mac hardware to run it.
There was also the comment about the person being required to use Windows or that he worked from Microsoft. Actually could have been considering it was a flight leaving Seattle!
And while I'm on the subject of Mac's, see Michael Cote's writeup on tips for a new Mac user. A good read.