Oj has an extremely large API that I have no intent on emulating in the default json gem, things such as "SAJ" (SAX style parsing), various escaping schemes etc.
My goal is only to make it unnecessary for the 95% or so use case, so yes, Oj will remain useful to some people for a bunch of uses cases.
Sax style parsing is a godsend when dealing with large files, regardless of json or xml. It's indeed what made me switch to a different json library in a Ruby project of mine (I'd have to look it up, but probably to oj).
