My slightly less positive feedback would be, it seems dodgy that it uses personatest.org instead of persona.org (and there's no website at www.personatest.org verifying its legitimacy). Kind of makes me anxious that I'm being phished. Any reason for this? You surely don't want people getting used to entering their Persona credentials at sites other than persona.org.
Otherwise it seems great :)
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Error Type: server is too busy
just two days ago I tried to install everything so I could be my own browserid provider. Turns out that is not really easy (yet). Even if I got quite a bit and was able to run https://github.com/mozilla/browserid-certifier on my server, I never was able to talk to it via curl (the example they have just crashes it) or from a PHP script (I always got a 400 Bad Request). That is mostly because I didn't get how "pubkey - Object compatible with JWT public keys." should look like.
In the end, after a days work I gave up because it was already way after midnight. I hope in the future there will be single file-php-script which I could call from the HTML pages I need to provide which would do all the signing, etc. for one-person browserid providers like I want to become.
Also, the reason the server is busy is because Tin Can currently needs a forked version of Persona, so it's not running on the production infrastructure.
Just drop a JSON file on your server and you're your own identity provider.
Really? Mozilla Persona doesn't support Firefox 23.0.1?
EDIT: BrowserSupport.getNoSupportReason() == LOCALSTORAGE_DISABLED.