So I got my Google Wave account last week and promptly invited 8 of my closest friends (ie the first 8 people that asked me for an invite). I've been on a couple of waves with Steve Anderson (Solutions Architect at Salesforce.com Foundation) and Jon Mountjoy (Community Manager & Editor-In-Chief at Salesforce.com) and Steve came up with an interesting use case for Google Wave.
Steve started a wave for a new blog post he wants to write regarding development best practices with Salesforce. I'll keep the exact nature of the post under wraps but it's going to be awesome! So Steve added me and Jon to the wave and started working on an outline for the article. At some point in time he decided that we weren't smart enough for his topic so he added a couple of other developers to the wave. Everyone started adding notes to his outline and code and his article began to take shape.
I actually saw the wave about a day late so I was able to join in midstream and replay the wave to catch the flow of how the conversation evolved. Google Wave was built for collaboration and it's pretty effective.
My wave account is firstname.lastname@example.org if you want to add me.