Features: - json-rpc errors return a more standard error object. (thanks to Gavin Andresen) - json-rpc command line returns exit codes. - json-rpc "backupwallet" command. - Recovers and continues if an exception is caused by a message you received. Other nodes shouldn't be able to cause an exception, and it hasn't happened before, but if a way is found to cause an exception, this would keep it from being used to stop network nodes.
If you have json-rpc code that checks the contents of the error string, you need to change it to expect error objects of the form {"code":,"message":}, which is the standard. See this thread: http://bitcointalk.org/index.php?topic=969.0