One of the dangers of using pre-release software is the breaking changes that inevitably come along before the final version.
The number of breaking changes between WPF beta 1 and WPF beta 2 were enough to discourage me from continuing on that platform until release. Actually I still haven’t had a chance to get back into it, but I will. Joe Stegman of Microsoft has posted the first of what I’m sure will be many breaking changes for Silverlight. You can read the blog here.
Keep in mind that even though he’s posted this list, don’t think that this list is a final comprehensive list of breaking changes between Silverlight beta and the RTW version. Expect more breaking changes to come.