I wanted to warn you regarding two bugs of the Winter '16 Release:
When creating a new user, after filling the details and pressing the "Save and New" button, in case you got a duplicate User-Name (or nickname) and you correct it to a unique name; and press the "Save and New" button again you will still get a duplication error and a new user will be created (behind the scene). This is very confusing, and may cause multiple users creation since you constantly gets this error (regardless the uniqueness of the new name).
When creating a new "Connected App" configured with OAuth, and press "Save" you get a "URL not found" error. Although the Connected App is properly created.
If any SalesForce R&D team members are watching this post, please address these bugs.