A few new OAuth-related API features.
Firstly, there is now the concept of scope. So if you want to do things like spy on a member's private messages or chat on their behalf, you now need to pass in the required scope (details in API documentation) to ask for more than just basic privileges.
Also, members can go to their profile to see exactly what outstanding access tokens exist for their accounts, in the same place as they can deauthorize.
Also, long requested feature ... You can now change your secret token and delete existing applications.