Out of those, it will be SL. Lively might have potential if they allow user-produced content, but it isn't at all clear to what level they will be doing that, and when. In any event, pretty much every single comment I have seen from "real people" so far on it has been either "I can't get in" or "I can get in and it's boring". I don't really know Vivaty but it just looks like the usual no-user-content "avatar chat" thing, as does Twinity. People have been able to customise avatars for many years now and there have been a number of IM systems with avatars involved, only, the traditional ones are still dominant. Without really having things to do which involve virtual space - not just running a few emotes, or panning around a 3D picture, but actual interaction between avatar and environment - virtual worlds are useless processor hogs. And a lack of user-generated content restricts what those things can be, drastically restricts the point to the user of having a virtual world at all. Why go in to see the same furniture and clothes and avatars? Why not just use MSN if you want to chat?