Sun should have built affordable Mac mini-like SPARC T1 or T2 desktops to foster multi-threaded application development they were uniquely well positioned to take advantage of. Almost nobody will buy a rackmount server just to explore some new idea, but a lot of dedicated nerds would buy a Windows-proof desktop running Solaris if only because it's really cool.

And no. Macs are not the new Unix desktop of choice. The portion of Mac users that are aware of its Unix heart is pretty meaningless. Most Mac users buy Mac because it's pretty and just about every other Mac user buys them because they work well.