I don't think this negates the fact that SIP is not an "emerging" protocol. The protocol has emerged a long time ago. Many people have not heard of it, because they're not nerds. People have used the PSTN for decades, but most have never heard of SS7, either. Does that make SS7 emerging? Hardly.
Now, SIP having issues is a whole other topic. In the famous words of a friend of mine, "SIP sucks. It really sucks. But, it's what we have." SIP is not the best solution for migrating the world away from the PSTN, but it's an acceptable first step. Anything beyond basic voice presents challenges for SIP. Hell, even basic voice calls present challenges for SIP. Suppose my phone prefers G.729 and yours prefers iLBC and does not support G.729. If I call you, my phone would offer G.729 and your phone would reject the call. Well, that's pretty useless, isn't it?
So, my phone will then try to place a second call, this time offering G.711. Your phone probably supports G.711, so we can communicate. However, my phone might also support iLBC, but that codec would never be selected since I have no idea what capabilities your device supports.
In this respect, H.323 is significantly superior to to SIP. H.323 is also better for video, since video codec negotiation is a much more complex exercise. It's important to have a good capability exchange mechanism.
And, we're getting to a point now where anyone can set up their own H.323 video service that runs "over the top" on the Internet. I can be reached at h323:
paulej@packetizer.com or h323:
paulej@cisco.com. The former is powered with a GnuGK and the latter is powered by Cisco's VCS and CUCM. Note that some people still have NAT/FW issues, but there are solutions to NAT/FW traversal. We have information on how to set up and manage your own H.323 services interconnected with the rest of the world at
http://www.h323.net/. Spranto also provides free calling services like Skype for those who just want to download the client and give it a try. It's free, too.