found this in pcmag.com, heres the most interesting parts;
'As for activation, Brown said users could expect a return to the familiar activation scenario. Windows Vista, like XP, contains an electronic list of the components within the PC, which it turns into a code, or hash. If a user adds or subtracts too many components, the hash will change enough that it will signal the need for another activation, which can be done either online or via telephone.'
and in particular this;
'Vista, however, will apparently be a bit more tolerant of the DIY community: "Windows Vista is more intelligent and a bit more lenient than Windows XP around hardware tolerance,"'
Seems all the fuss about tougher activation rules might be overblown and if the article is correct then the activation system of vista should be at least very similar to XP.
You can read the full article here http://www.pcmag.com/article2/0,1895,2087792,00.asp