I think there's a tremendous opportunity around more efficiently bringing real-time attributes to many applications, including multi-media. The silo's of mail, IM, Tweeting, etc are getting too clumsy and unwieldy to manage. That's why I like the appeal of Wave.
Executing on a market opportunity is, of course, a distinct step from seeing it. Here's a well thought first impression of Google Wave written by Orli Yakuel.
This is an early beta and it will be interesting to see how the product evolves. On that topic, and as a stunning contrast, I just downloaded the most recent version of Powerpoint viewer (2007). Imagine freezing a crippled application for 2+ years? MSFT's DNA is totally different from successful web based companies. I suppose if I was charged with protecting a $58b revenue stream and 36% operating margins, it would stifle my innovation too....notwithstanding the MSFT haters, I would love to see the passion return.