4. You state that 2-3 years of 'shelf life' should be OK for specialized pro level systems. What do you think the quad G5s were when they came out? You just wiped out your whole argument.
From a business stand point yes; but not everyone in the Pro market works for a company; many are freelance and probably can't afford new systems every 2-3 years. Although a "Pro Level" machine ought to be supported longer than consumer system, yes?
And yes comparing a laptop to a desktop is not really a fair fight; but then again I don't have modern PPC hardware to stack against the 4-core modern Xeon. I am pretty certain IBM could spank Intel if the price was right.
Don't get me wrong though, the Intel transition was overall a very good move by Apple. Everyone seems to want Mac laptops these days.
-mark