Configuration assumptions for running Windows Vista are not accurate at all.. not even close... first thing, Micrososft still doesn't know will they run Vista with DirectX 9 or maybe even 10.
Besides, what is so strange with more powerful machine requirements ? We do not live in 1986 any more, of course we have to go with the flow. Everyone should be aware by now that you are not gonna be able to cope with new modern programs/applications/OSes on some old 386SX... of course we have to upgrade our machines from time to time. If someone is unable to do that because of financial situation, that's understandable, but in that case, again because of his/her financial situation he/she will not be able to buy Vista, so no point in crying anyway.
The only real new requirement will be more RAM and video card. It's not like anyone is asking us to buy a Cray to be able to run Vista. I just bought myself ATI graphic card (hardware support DirectX 9) under $70 CAD, and all those prices will go down even more... that's for sure. Vista works perfectly on my machine with that card installed and 1Gb DDRAM. All real time graphic effects, transparency, bloor, all animations, everything runs perfectly... so as you can see, no need for some turbo expensive GFX card to be able to run Vista. Of course if you are one of those crazy gamers, and you simply have to have a video card that costs around $600-$900 CAD, that's another story and not Vista's problem...
New technologies brings us more powerful things... more powerful things requires more power... simple as that.