Kudos to UC Expert Phil Edholm for leading the discussion, and we had a lively debate earlier this week during our podcast recording. I have long contended that the underlying technology is perfectly fine - the real problems come from not properly supporting VoIP in the network, as well as a basic lack of understanding about how VoIP behaves in a data network. Throwing more bandwidth at VoIP isn't the answer, and my views were echoed by the group, so it's not just me waving the flag.
Everyone struggles with this issue, and I hope you check out our podcast. It's running now on our portal, and my comments come at the 34:16 mark. In addition, I highly recommend you review Phil's No Jitter piece that prefaces the topic. While it's highly theoretical, there's a lot of technical insight about the dynamics between TDM and IP traffic and how this impacts networks.