write(), print(), println() now return size_t (and don't use negative values to signal errors).
Print adds writeError() for checking for write errors, clearWriteError() to reset the flag to false, and a protected setWriteError() for signalling errors.
http://code.google.com/p/arduino/issues/detail?id=598
The switch from checking _sock against a default value, combined with the checking for unconnected clients in status(), broke the Client. I went back to checking the value of _sock against the default and removed the _connected member altogether because it was redundant (and therefore needed to be kept in sync with _sock).
