We just pushed up a lengthy forum post regarding the changes coming in Beta 2 for xUnit.net. There are quite a few high impact changes, so if you're using xUnit.net, it would be worth reviewing the post in preparation.
It is our hope to post the Beta 2 bits sometime in the next week. For those who are anxious to start looking at the changes, the trunk of the source tree has most of the changes in it already, including all those listed in the forum post.
I personally want to thank everybody who helped contribute with feedback on Beta 1 (there are too many to list). Please keep the feedback coming!