Skuzz,
I'm not sure it's all marketing. I remember from waaay back, how frustrated I was that playing mp3s in the background would make WB stutter. I still can't reliably play music on my computer while playing games.
A second cpu would make that happen. Not only that, I could keep other background stuff such as the occasional dvd or video encoding effort going while gaming. Or I could run a virus scan without it either grinding my machine to a halt or taking 8 hours, take your pick.
So I see a lot of benefits to a second cpu core, even in as rough a form as it is right now and without individual software packages being written to take advantage of the second core.
Don't take this wrong, but sometimes too much knowledge is a bad thing
As an example, you've said several times that 64 bit windows will absolutely kill gaming however I've seen a crapload of gaming reviews using beta 64 bit drivers on the early 64 bit windows releases that show equivalent performance. Less than 2% gain or loss across the board. You're right, microsoft has done a bunch of stuff with 64 bit windows that is pretty evil to a programmer or system administrator, but to the user it really isn't going to make much of a difference right away. It's like the doom and gloom we all saw when the original pentium came out. I remember reading 10 articles by experts like yourself, shouting up and down that the pentium was slower than the 486 it was replacing. Yet my first pentium was as fast or faster than the 486 it replaced, making that another case of knowing too much being a bad thing.
Anyhow, it's easy to trash talk the dual core cpus out now because you're right, they are rough early versions of a concept that needs some serious work to take advantage of. But even in it's rough form, it sure as hell won't hurt and there are definately situations where it can make a clear positive difference.
It's the same with the intel vs. AMD argument... Intel proponents will claim that AMD systems will never approach the stability of an intel system, but frankly once I quit fuxoring with my A64 system and set everything back to default, I haven't had a single BSOD, crash, spontaneous reboot, or other system failure that I couldn't trace back to poorly behaved software or a windows bug. And it's as fast or faster than Intel systems that require more power and cost more. That tells me that a quality AMD system is at least as reliable as an intel system of the same quality, because there is no measure of reliability that beats "zero failures". Put together crappy parts and you get a crappy system, regardless of if it's AMD, Nvidia, VIA, Intel, SiS, Motorola, or PowerPC.
Anyhow, that's my rant against the man for the day