@andstatus Sorry I didn't answer because I didn't have time and then forgot :)
I think it would be better to use the AS json data than the Twitter json output! It should have the same information and more of it too!
So far I've relied on that data is properly converted from the internal data format (which I make sure works in the AS in Atom output) to AS in JSON. So far I haven't broken anything to my knowledge, but since it is less used overall there is a higher likelihood of unnoticed issues.