True (on desktop), it looks like a big change but it really isn't. Nothing below the header area has been changed, other than the font, which is barely noticeable.
Also keep in mind that the change is intended for the base communities (communities.win), we didn't set out to change The Donald's style specifically. The base CSS was horrific before, now it will be acceptable (in my opinion) once this update is finished.
You might be referring to this incident.
No, users shouldn't have been fully logged out.
If they were fully logged out, they should try multiple incorrect passwords before entering the correct one, to ensure that we do still know the correct password. However be aware that trying too many passwords may temporarily lock you out silently.
The delay at the start of a session (or every 60 minutes after a session began) is a flaw with our old SSO process, which this update addresses. The "logged out but not logged out" issue should be resolved with this update, too.
Abandoned how?