No update at this point. 5 months and counting. Oh well.
Unfortunately I have started to see a further deterioration of shared notebook functionality. Specifically my wife (also a premium subscriber) is no longer able to merge notes within our shared notebook. I can merge notes, but I originally created the shared notebook. When she tries to merge notes, the Mac version of Evernote doesn't even show the option. Also when she moves notes into the shared notebook, it copies the note in, instead of moving it. So she ends up with 2 copies, one in the the original notebook, and 1 in the shared notebook. One silly perk of this functionality is that she doesn't get the Move warning referenced in this thread!
The challenge for us is that solution to our problem is rather obvious. And it doesn't involve upgrading to the business version for us to pay $15 * 2 people * 12 months. It actually involves us becoming a single user and saving 50% on our premium bill.