I don't really get it. I use contacts on my phone + iMessage, this seems to be just a slightly more featured contacts manager? But, comes with a huge drawback that everyone else needs to be using it as well?

I would like an app where I can manage my friends / family lists, and then be able to text multiple people at once, invite them to events, etc. Those are the useful features I see from social networks, but are not well replicated right now outside of Facebook.

I typically manage all my contacts thru Google, and that has some features for merging duplicates, portability across devices/gmail, and also some list features.