tedster - 7:56 am on Apr 10, 2010 (gmt 0)
The complete details are not published, but we do know that they are using Toolbar data. Here's another thread on the topic - Google site performance measurements for international sites [webmasterworld.com]
Also - see the new blog article from Matt Cutts:
The main thing I want to get across is: don't panic... we still put much more weight on factors like relevance, topicality, reputation, value-add, etc. — all the factors that you probably think about all the time. Compared to those signals, site speed will carry much less weight.