Yup, I've done a bit with 9.2, and it accepts JSON just fine (although not with automatic string conversion) but it's a short road to wishing the data were in standard tables and columns.
Cool, thanks. Last time around I used a pg-driver-specific datatype to hold the parameter on its way through sql2o, and felt rather guilty about doing so.
insert into my_table values ($$ json_goes_here $$);
Works for all stringy things.