It used to work but I had not tried for a long time.

It was broken with 0.9.15 so I updated to 0.9.16 but it is still broken. It fails with any TLS settings (required or not, ignore or not the certificate errors)

The part of the log that I guess is useful:

wocky-DEBUG: 20/08/2010 12:19:44.471628: wocky_xmpp_writer_stream_open: wocky-xmpp-writer.c:298: Writing stream opening: <?xml version='1.0' encoding='UTF-8'?>
<stream:stream xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams' to="gmail.com" version="1.0">
wocky-DEBUG: 20/08/2010 12:19:44.504188: _start_element_ns: wocky-xmpp-reader.c:430: Received stream opening: stream, prefix: stream, uri: http://etherx.jabber.org/streams
wocky-DEBUG: 20/08/2010 12:19:44.504200: _start_element_ns: wocky-xmpp-reader.c:443: Stream opening attribute: from = 'gmail.com' (prefix: <no prefix>, uri: <no uri>)
wocky-DEBUG: 20/08/2010 12:19:44.504213: _start_element_ns: wocky-xmpp-reader.c:443: Stream opening attribute: id = 'B77228F6C0B53FFB' (prefix: <no prefix>, uri: <no uri>)
wocky-DEBUG: 20/08/2010 12:19:44.504221: _start_element_ns: wocky-xmpp-reader.c:443: Stream opening attribute: version = '1.0' (prefix: <no prefix>, uri: <no uri>)
wocky-DEBUG: 20/08/2010 12:19:44.511205: _end_element_ns: Received stanza
* features xmlns='http://etherx.jabber.org/streams'
    * starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'
        * required
    * mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'
        * mechanism
            "X-GOOGLE-TOKEN"
wocky-DEBUG: 20/08/2010 12:19:44.511353: _write_node_tree: Serializing tree:
* starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'
wocky-DEBUG: 20/08/2010 12:19:44.551335: _end_element_ns: Received stanza
* proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'
gabble/connection-DEBUG: 20/08/2010 12:19:44.662235: connector_error_disconnect: connection failed: WOCKY_CONNECTOR_ERROR_TLS_SESSION_FAILED (#7): TLS handshake error: -59: GNUTLS_E_INTERNAL_ERROR
gabble/roster-DEBUG: 20/08/2010 12:19:44.663531: gabble_roster_close_all: closing channels