I got an invite from my brother, who was one of the elect 100,000 who got the first round of invites from Google. At first, it was exciting -- I get to be one of the first to experience the next revolution in technology! -- but the first question I had, once I got a look at all the features, was: So what am I supposed to do with it?
To be sure, I can certainly see how Wave could become huge: It really does integrate email, IM, online collaboration à la Google Docs, and no doubt many other things into a seamless whole. (I especially like how it devises a viable alternative to Evite.) The proof, however, will come when many other people -- and especially those whom you work with and socialize with -- start using it as well. Right now it's merely a curiosity, not an email or IM killer.
It's also buggy as hell: I tried using the Bloggy Wave robot to write this post and wound up losing the whole thing. It's just as well: Turns out Bloggy only sends waves to a special wave blog, not existing ones. Nevertheless, Wave shows a lot of promise, as the folks at Lifehacker demonstrate.