I've updated all my extensions for Beta 2. Here are descriptions of the changes, as well as links to the source for each on github and the extension on VS Gallery.
This was the only one that was somewhat substantial. There were essentially two changes:
First, the classifier that underlines the text has been rewritten (very slightly) as an ITagger<ClassificationTag>, so that the provider can be rewritten as an IViewTaggerProvider. This is going to get its own blog article, but the short story is that if you are writing a classifier/tagger that is consuming other classifiers/taggers, you should write it as a view-specific tagger to avoid accidentally using an aggregator that uses another classifier/tagger that uses your classifier/tagger that uses an aggregator that uses...ad infinitum.
Second, the mouse handler had some ugly logic for getting a service provider and getting the global shell command dispatcher. That has been simplified down (from ~20 lines to 1 line) to use the new [Import] System.IServiceProvider in Beta 2.
This one was really minor. The only change of note is that IEnvironment is gone in Beta 2 from everywhere, so you can just delete all references to it and its namespace (it has ApplicationModel in it, but it should be obvious if you re-compile an extension you wrote against Beta 1).
This is the extension that I blogged about yesterday.
Oh, and I also wanted to add: I heart git/github very, very much. Internet props to all them git/github people.