Yep, I picked up a copy on Saturday and upgraded Sunday. It, so far, is OK. I have had problems with mail, and a couple of other minor issues, but so far so good. However, I have not seen (haven’t looked hard) much difference.
Ars Technica has a detailed report on the changes.
If you're not a developer, the changes aren't that big (that's why it's only $29). If you are a developer, they're pretty huge.