XML-RPC should be a defacto standard in all miners! I'd also like to see JSON-RPC as it seems to be the protocol favored by the majority of bitcoin projects. I patched guiminer, but I'm now thinking it would be better to implement directly in phoenix/poclbm (https://github.com/entens/poclbm/commit/7420e4560ae5517b01d0a758b15b16a6874cba4d#guiminer.py).