Long polling and and web sockets are not such a good fit after all, moreover the implementation is not ready.
"not good fit" hmm, I'd say that if you can use XMPP over plain TCP then this is the preferred solution as it does not come with an additional overhead.
BOSH only advantage compared to XMPP over TCP + XEP-198 is that it could be successful when most outgoing connections are blocked/firewalled.