I literally cannot use the Metro one as it tries to force me to merge my Skype account (of which I have several) with my Live account (of which I have several).
I also use my Skype account in less secure environments like on insecure airport WiFi than I do my e-mail/Live Account, so the last thing I'm going to do is merge them.
If my Skype account was ever stolen then no big deal, since it is "free" and I have no stored Credit Cards. If my Live Account(s) were stolen then that is a very big deal.
If Microsoft forces us to merge these accounts across the board then I might have to reconsider my usage of Skype like I currently do. I might check out Google+'s video chat features instead.