Of course the reason that what's going on now is different from anything before is Apple moving mainstream with Intel processors and OSX (underlying Unix). It's the shell-game, and confounds people who still look for reasons to hold out against Mac.
Couple this with the FUD factor of Vista delays, and an absolute void of any big upgrades this coming Holiday season except for the Mac, and you've got an environment much more like the early 80's and the days of 16-bit processors where any one of them could suddenly seize sizable market share.
Apple Market Share to Explode?