Hi John...
I've had a few years working with VCON products...
VCON have (IMHO) has best by a long way implementation of H.323 out of any of the mainstream products out their. They are GOOD (network technology wise).
The only downside that there is with VCON is that although technically their great, they often sell them with crap camera's that lower the overall quality (which is all the end-user cares about), and personally I'm not a big fan of the interface.
Hope this help