I didn’t write it but I just read it and, at 69 pages, it’s as comprehensive an inventory as you’re likely to find.
The paper describes Silverlight 2 and the coeval version of WPF. Microsoft has been rapidly whittling down the differences between the technologies and enriching both with new releases due in a matter of weeks and radical changes slated for SL 4 in 2010. This paper forecasts some of the changes that arrive in SL 3 but there is much omitted; we must hope that Microsoft continues the funding to keep it current.
Nonetheless, it is a superb baseline and should retain its relevance for at least another year even in its current form. Highly recommended.