Sun and Apple are both strong brands within different market sections. Sun is company- and serveroriented and Apple is niched towards consumers and desktop. Yes, I'm aware of that Apple sells server software and hardware and Sun has tried to enter the consumer-/desktopmarket by offering there own desktop OS and StarOffice, but these are not the markets where they are at best.

From my point of view they seem to complement each other quite well, one niched towards companies/servers and one towards consumers/desktops. Why not knit the pieces together?

As you know, monocultures are not good, and at the time being Microsoft is unparallelled in market shares on the desktop, less so on the server side. But by joining forces Sun and Apple could perhaps compete with Microsoft about market shares for servers and desktops. 

I believe that if one is to succeed to compete with Microsoft one has to offer a tightly integrated server and desktop solution with good tools for management and with professional support. In that case perhaps some companies dare to throw out Microsoft in favor of an Sun/Apple solution.  I would certainly like to see an Apple on my desk and a Sun in the server room.