Started examining this for a quick fix. When I explicitly use json/pure in money rspecs all the encoding issues go away. json-java fails and I suspect the native extension might need some additional love for string creation in 1.9 mode. Currently, it seems to make all strings it creates as ASCII-8BIT when the source string starts as UTF-8.
This particular issue should probably be replaced by multiple individual issues (I suspect for each native extension), but I will leave it open until I get some traction on json-java.