I re-flashed my N950 with PR1.1, then added Twitter (which I couldn't add at all after the OTA update, hence the reason to reflash), Google and Facebook accounts from scratch (no backup restored - totally stock).

After reflashing, my Google authentication is fine, so my Availability is online 100% of the time, but Facebook availability repeatedly falls offline for no apparent reason, complaining of an "Incorrect password". Manually putting Facebook back online works only at the second attempt (maybe sometimes a third attempt, but normally the second, and never the first). It's extremely annoying, particularly as you don't realise you're no longer online for Facebook once you have a second account also with presence, and I'm assuming it's one and the same bug we are both experiencing.

Also for some users when adding accounts, they can only add an account at the second or third attempt. Seems to me like there's something fundamentally borked in a shared authentication library that means authentication only ever works at the second or third attempt. And totally screws up automated processes, such as Availability.

Konttori references this issue in his blog post:

I sincerely hope it has been solved in PR1.1 for the N9 - it's been knocking around for months now, and reported many times. Sadly, it's definitely NOT fixed in PR1.1 for the N950, which I hope is just a Beta and more fixes will go into it before being rolled out to N9 users.