One major problem that Apple has right now is that they've lost most of their technical advantage over the years. Now that they've faltered in performance, there is not much left for them to sell the platform on.
Back in the day, Apple had significant functionality and usability advantages over other platforms. PostScript, LocalTalk, and laser printers were common things on the Mac platform back when PCs were still using daisy wheel or dot matrix printers. LocalTalk was much easier to use and configure than NetWare over coax. NuBus offered better performance and was easier to configure than ISA. Apple offered multiple, high resolution, 32-bit color support on the Mac back when CGA and EGA were the status quo. The Mac had an arsenal of great software not to be found on the PC. And the Mac of course, at that time, had a significant usability advantage over DOS or Windows 2.0/3.1.
However, those advantages have all evaporated due to modern hardware, software vendor migration, and the advent of the Windows 9x interface. So what value does the Macintosh bring to the table in this day and age? Well, OS X is a technical marvel (and has been for a while, even back when it was NeXTstep). However, providing minor OS nicities, a good development environment, and a slick GUI won't get you all that far when software like the Adobe apps are written to accomodate the least common denominator (Windows). In cases like that, corporate IT looks at price/performance and the Mac platform falls down right now on that point. Sure, consumer sales and marketshare are great. Apple has done a good job of catering to that segment recently. But let's face it, corporate spending is where the big money is at, and as long as Apple is uncompetitive on a spend basis, they're not going to crack that market. (Not only that, most office computer users buy for home what they have for work.)
So where does this leave us? Well, considering that the processor wars are going to be neck and neck between PPC, x86, EPIC, and x86-64, it's unreasonable to assume that Apple is going to garner a huge advantage in speed. And as long as they keep using commodity PC components and standards as their mainstay, other parts of the subsystem aren't going to rev past their counterparts. What Apple needs to do is to differentiate themselves in a way that makes the price/performance issue irrelevant. They need to find the next DTP. Something that they can bring to the table that another company can't emmulate in a short period of time. DTP brought this first. Multimedia and QuickTime did it again. Granted, other companies managed to make up for lost time, but for a while, Apple provided something that you couldn't find anywhere else. And people were willing to spend to get it. I think this is what they're going to have to do again if they want to get back to that long lost two digit marketshare.
Just my .02
-K