I've been thinking about this post for a while, but unfortunately Rolling Stone beat me to it. It makes some interesting points, but it doesn't really target what I was thinking.
Apple is VERY proprietary. Now, this is a double edged sword. Apple components (iPods, Wireless Routers, Music Players, etc.) all play very well together, and can be setup very easily. However, many of these systems are very locked down.
iTunes Music Store -> iTunes -> iPod is a closed system. You can add your own MP3s to iTunes (prohibiting that would be a non-starter for nearly everyone), but beyond that, you can't really swap any of these parts. Want to buy from another music store? Too bad. Want to listen to your music on a different device? Too bad. Want to sync your non-iPod with iTunes? Too bad. There is no doubt that this drives the popularity of the iPod. Syncing your iPod with iTunes is easy, and much better than the compatible experiences. Using a Dell DJ, even with additional 3rd party software still doesn't compare.
Contrast this to my D-Link Media Player. It comes with its own server software, but there are also several open source servers I can use to stream music/video/pictures to the device. The same is true of my Rio Receiver. But I keep my music in iTunes, so I had to write a utility (iTunes Export) to share my playlists with these devices.
The iPhone is another example. In a recent post I pointed out some reasons why I don't think the phone is great for me. There was a lot of excitement about the phone initially, but I find it interesting that while they tout that it runs OS X, it is also a closed platform, or at least its undefined how 3rd party apps could be added.
The amazing thing is how Apple gets a free pass on this. Microsoft is the 'evil empire' partially because they are said to leverage their market domination in one area (Windows/Office) to compete unfairly in others. I've always contended that developing using Microsoft technologies can be great as long as you stay on the Microsoft path. Use all the MS tools and follow their conventions and you can be extremely productive. With Microsoft, at least you CAN stray off the path.
I think it will be very interesting to see how Apple copes with its increasing market share and product line. I expect there to be a backlash at some point as Apple goes from being a cool niche to mainstream. I think we've already started to hear a growing frustration with Apple, and time will tell whether they will be able to handle the increased popularity.
That said, I've seriously considered switching to a MacBook before, and now that they are on the Intel platform it is even more appealing. OS X is becoming a very popular OS among Java developers, and I even have a friend who develops on Windows running in Parallels on his Macbook Pro. For now, I'll stay an Apple watcher from the sidelines.