Heads up: another techie entry.
Even 24 hours after the fact, I'm still recovering from the shock of Steve Jobs' bombshell.
My engineering-centric take on things (from someone with both low-level X86 and now PPC experience): The reaction of the Mac crowd seems to be evenly split between predictions of doom, and optimism that this could be the gutsy move that catches Microsoft off guard and elevates Apple to the mainstream.
Personally, I disagree with both camps, and -- despite getting caught off guard myself and it being something I never would have predicted myself -- I just like to think of it as a natural evolution given the evolution of hardware (more below). Specifically, on thinking of it some more, I predict the status quo with regards to Apple's market share post Intel transition.
** Apple's hardware "edge": OS X on generic PCs -- it's not a matter of IF, but WHEN. Considering the fact that people have already managed to get Windows (somewhat) working on something as non-PC as Xbox, I'm expecting to see OS X/Intel running shortly on all our crappy no-name boxes, despite what Apple might wish.
Despite this, I don't think it will necessarily diminish Apple's hardware revenue stream (but it certainly won't increase it) -- witness the fact that iPod sales aren't exactly in trouble despite everyone and their dog in the electronics world having their own cheaper MP3 players. Apple has always been known for its quality (certain iBooks excepted... =P) and industrial design.
Also, with the more carefully controlled Mac hardware combinations, they can hopefully avoid driver hell that plagues even the best PC installations due the myriad of hardware possibilities -- anything else is just "not supported" officially.
** Why is it natural? The gap between RISC (eg, PPC) and CISC (x86) is diminishing; internally, the latest x86 chips all translate the x86 ISA instructions into RISC-like microcode anyhow. Furthermore, RISC code by its very nature takes up more memory, and that is not getting faster nearly at the same rate as the chips themselves. Thus, transistor space which is saved by less complex decode logic on RISCs is taken up by larger L1/L2 caches and larger register files.
Furthermore, pipelining and out of order execution are run of the mill now, these days, and you're going to get a complicated chip, RISC or not.
So with these things more or less equal these days, consider Intel has economies of scale in R & D and production; development costs can be amortized over hundreds of millions of units, rather than a few million. This is solely because of Microsoft and it's no fault of Apple's own, of course. I certainly don't have the numbers myself, but despite the fact that I think that Jobs is certainly someone that sometimes can spew out the Kool-Aid for the masses in the cult, this time I do agree with him that economics alone are a compelling reason.
** Is RISC dead? There's a lot of crap being spewed on various sites and forums predicting this after today's announcement. Far from it! Where RISC shines are embedded/consumer apps like game consoles (remember, IBM is making chips for all 3 next gen platforms), or high-end stuff like supercomputing. The reason is that for those, your hardware platform is fixed, and they aren't subject to the endless upgrade cycle that your desktop PCs are. You compile your code, and it's going to be running on one CPU type, so the compiler can do instruction scheduling and other tricks for a specific type, shifting it from the hardware (one of the original touted advantages of RISC that our computer architecture profs were always touting in our classes).
With a mass-market software app for Mac or PC, you can't really do this, less your careful tuning work goes to naught with the next processor release.
** Finally, the million dollar question: Will I still get a Mac and make the Switch myself? If OS X is hacked to run on non-Mac hardware, probably not... but I would definitely get a copy to play around with and maybe do my email and websurfing on.
Wait... I take that back. I'm in the market for a new laptop to replace my 5 year old T20, and if I can dual-boot Windows and Mac OS X, I'll be the first to get a future Pentium-based Powerbook. =D
Anyhow, to everyone, I say... nothing to see here, move along. Nevertheless, thank you Mr. Jobs for giving me something to think about on this otherwise lifeless Tuesday. =)