The XMeeting project has been slow-going but fortunately release 0.3.4 from July 2007 has been very stable. Over the past year and a half, Apple released some Quicktime updates that caused a funny distortion of the local camera view. Otherwise, it's been solid.
Near the beginning of the year, I found release 0.4 preview 1 posted on Sourceforge and tried it. Couldn't keep it running. Preview 2 was released at the end of January and seems to be much more stable. It fixes the local camera view bug, has a cleaner Preferences panel and seems to have some updates for H.264. I'm still not connecting to the Polycom MGC-100 at any higher protocol and resolution than H.261 CIF, so that incompatibility has not been fixed. Still, I am pleased to see progress in the XMeeting program and a fix for the video bug.

Hi Bill,
I see there's no new XMeeting, but I'm wondering if there have been any other developments since this post. I've found that the HDX 8000 in 519 Wartik is sending H.264 (352x240) to XMeeting, but I can't get any higher resolution. Unfortunately, the computer at the Polycom end is too blurry to read on the XMeeting end at such low resolution.
Thanks,
--nate
I have also experienced the same with only getting low res. Furthermore many conferences I've joined have utilized H.239 dual-streaming camera + content which XMeeting does not support, leaving me quite in the dark. So while it works for casual video conferencing I've not been able to make the most of it for our business functions.
Surprisingly, XMeeting seems to be the only free/open-source H.323 + SIP video software out there for Mac. That's sad.