I think part of the reason Buzz hasn't caught on is the privacy debacle at the start. It left people with a bad association with Buzz, and that's not something that's easy to shake.
Wave I see mostly as an experiment. It can do some cool stuff, but I've never really had a use for it. I did see it used for streaming commentary the Google I/O keynote (courtesy of Lifehacker), and it worked fantastically for that. In fact, I'd say that was the nicest live coverage method I've seen. However, I personally still have not found a use for Wave.
If Buzz had had a really compelling user experience and killer features at the start then that's what the early media reaction would have been about.
Instead they launched a half-baked product, with high expectations because anything Google does immediately has a high standard to meet, and that let the unforced error they committed with privacy dominate the news.
It's certainly a failure from just how much it was being hyped up as "the next internet" etc.
Yeah I think quite possibly both are superior technically, and I think integrating Buzz with GMail was a good move, but I think they'd do better adding features and iterating gently toward where they want, rather than suddenly introducing new things that confuse/alarm users.
Personally? Lack of integration in clients. Everything hooks into Twitter. Everything hooks into FB. Extremely little hooks into Buzz. I also want more privacy & organization controls than it offers, but I doubt that has a lot of impact outside geekdom.
From my uses, at least. If/when it changes, I'll probably start using Buzz more.
Wave is no mistake (yet), it's still under construction.
Also, it's a protocol, not that much a product. Also, the client-server protocol isn't even finished.
