Zune and iPod is not a PC versus Mac re-run
Back in the mid 1980s when the Mac burst on the scene to vie for dominance of the new desktop market with the PC, it was clear which machine was for business and which was for the home. The PCs were absolutely primitive compared to the Mac but they were open and they were backed by IBM, the business computing king.
Back then, no-one said Micosoft PC - it was IBM compatible PC.
Then Microsoft, with the help of Intel and some bad decisions by Apple and IBM, managed to sneak into the dominant position of first the business market and then everywhere else. Microsoft, as its name suggested, knew exactly what business it was in. Apple, which had by far the better operating system, wasn't sure and got slaughtered.
The online music space, however, is a totally different kettle of fish. Apple has shown the world how to dominate that market in a way the company never did with the Mac. It developed the killer model in a similar manner if not execution as Microsoft did with the PC running MS-DOS and later Windows.