I'm rather unimpressed with both. Wave is really cool technology. I won't deny that. However it's UI screams get lost in me. Buzz it much better but it's still more complicated than twitter and uglier than Facebook. It's this horrible middle ground.
Google wave is a godsend for teams of people who work together. We no longer have to exchange a million emails about a project topic. We all keep it into the wave.
Its not an email alternative. Its and adjunct.
You said it. Occasionally my team starts to fall back into the old "million emails, cc's and catchup email" pattern when suddenly somebody will say "let's move this to a wave" and suddenly everything becomes very simple and easy to organize.