SL - how to grab dispatcher, random tips

Q: how many dispatchers are there in one SL process?
%%A: 1, according to many c# guys. However, a lot of literature mentions "a dispatcher"

Q: can you get hold of the dispatcher from Any thread Always?
A: http://www.jeff.wilcox.name/2010/04/propertychangedbase-crossthread/ says not always

Q: which source is best to get the dispatcher?
A: Deployment.Current.Dispatcher is preferred over Application.Current.RootVisual.Dispatcher. See http://www.jeff.wilcox.name/2010/04/propertychangedbase-crossthread/ and other sites

Q: Is SynchronizationContext better than dispatcher?
A: http://www.jeff.wilcox.name/2010/04/propertychangedbase-crossthread/ says dispatcher is easier
A: http://dotnetslackers.com/articles/silverlight/Multithread-Programming-in-Silverlight-4.aspx demonstrates both.

Q: how many UI threads are there?
%%A: 1, according to many c# guys.