I think you're ignoring the fact that Apple's sole professional stronghold is the creative industries (graphic design, video editing etc.) If they crap on their customers in this area too many times, they might as well forget the professional market and give it all up to Windows.
While Apple is no doubt doing very well in the consumer area these days, it's debatable just how much more they can really do with the iPod. It plays music, it has a screen; where can it go from here? Are people really going to be buying iPods in the numbers they have forever? And what if a competitor comes out with something better. The iPhone is doing very well, but can they continue to innovate - at the moment they have more or less the only product of it's type, but there are a whole raft of companies playing catch up, and will be putting out similar products with competitive specs soon (Flash anyone?). Apple would be stupid to think that their consumer products are going to be around forever, and the next one out of the door might be a flop (Apple TV has hardly set the world on fire - so far, they've failed to do with TV/movies what they've done with music).
The point is, that the creative industries have largely remained fairly loyal to Apple for 15 years and there's no reason for that to change. Industry doesn't go through phases and trends in the same way consumer markets do. Apple need to sort out their strategy for their high end workstations, before their professional base looks elsewhere.