I am trying to implement this and coming across the same issue. This is over 2 years old per this discussion so I'm shocked - is nobody actually using this feature or are we missing something fundamental in the implementation?
I store data in json.channel_data, and I can retrieve it on the same device. On another device registered to the same account, the roku_pucid is the same but I get gibberish back in channel_data. It seems to be escaped with Unicode - are you encrypting it and requiring us to decrypt it? That's fine - tell us how.
This is a blocker - please respond.