Weird fact: an iMac G5 with a 17" display (when it debuts) is more than good enough to do professional 3D work on. Incidentally, it's also good enough to do slick video editing on, and iMovie and FCPE are there (now also Motion). I think Apple is marketing to people who have a few characteristics.
1) Middle/Upper income folks who are willing to pay a bit more for a better user experience. paying 500 more for a computer is not a huge deal if you have a decent income.
2) People who like to have fun with technology. No other platform offers as many entry level tools (the whole iLife bunch and more). This includes people who like to shoot a lot of digital photos or video. It's the whole digital hub concept. People are starting to buy into it.
3) Professionals in media and design.
The first two groups do overlap, but it's a huge market. Way bigger than 5% or whatever. Apple's problem is not really pricing. These are the same people who buy the 500 dollar option to get seats that warm up your ass. Apple's problem is the status quo. People who should consider macs don't, because of a stigma of uncompatibility that developed in the 90's.
But don't worry. Apple's market share and success will grow in the next ten years for the simple reason that us kids who have been exposed heavily to the internet weren't using computers much during the compatibility days (at least I wasn't. . . my dad had a tandy for a while. I wrote papers by hand when that was not the cool thing to do ) But anyway, the compatibility problem dies when the people who believe in it aren't young anymore.
So buy stock in Apple.