You can now get a stable h.323 IP PBX using PNX.
See our home page at http://www.file-sure.com/AsteriskPNX_proj/
With the feature rich Asterisk PBX and very good Openh323 voip support, PNX can be used for many innovative telecommunication services.
I am still working on a stable version using the latest Openh323, which will then add SIP into PNX features. Will be back with more good news.