When you get some invites you get a bit more use out of it but for now search for "with:public mountainbike" (or anything else instead of mountainbike) and you will find loads of public waves to play with.
Well, so far (in the absence of anything more useful) it contains my Christmas wish list, Our baby "getting ready, what do we need/need to do" list and my wife's Christmas wish list. Along with other waves so people can say what they have got me, without me seeing it and the same for my wife. All unnecessary and could be achieved in other ways but possibly easier (can just dip in when something springs to mind and it is recorded for whoever is interested to see).
Good alternative to email, eventually, possibly. Fun finding out though, if you like that kind of thing, which I do 🙂
Don't know what to do with it in the main. Unless you have a bunch of other people and a reason to collaborate on something it is just a toy really. An interesting and still buggy toy but I think I like it. I can see loads of potential for using with classes in school for instance, or arranging group rides/weekends away and sharing pics etc. afterward. Think it will become more useful as more people produce extensions/add-on's for it as well.