THE-QS 2008 Update
This year there has been only one methodological change, namely the separation of the lists in the academic survey section into international and domestic sections and then their recombination. This would probably work against universities that receive a lot of votes from their own countries and might explain why Hong Kong, Peking and several Australian universities have fallen quite a bit.
Also, it is likely that the geographical spread of the academic and employer surveys has expanded and that this has benefitted universities in Latin America, Africa and India.
The biggest change in the top 100 is that Washington University in St Louis has risen to 60th place from 161st in 2007. This, presumably, is because it is now getting a realistic score for citations per faculty instead of the 1 it got in 2007, when QS seem to have confused it with the University of Washington. I am a little bit suspicious though about these two places being next to each other in this year's ranking.
The University of Hong Kong has fallen from 18th to 26th, Peking from 36th to 50th, Nanyang from 69th to 77th, Melbourne from 21st to 38th and Macquarie from 168th to 183rd (I wonder what Dr. Schwartz will say about that.)
On the other hand, the National Autonomous University of Mexico has risen from 192nd to 150th, the Indian Institute of Technology Delhi from 307th to 154th and Chulalongkorn from 223rd to 166th.
One oddity that I've noticed is that Stony Brook University, which is an autonomous university centre of the State University of new York, has risen dramatically to 127th place from 224th, while the other three centres at Binghamton, Buffalo and Albany which are of equal or better quality do not even get into QS's initial list.