And Viber beats WhatsApp into the ground.
I've tried half a dozen SIP products. Many of them look attractive but they all suffer from two major problems;
- No single directory, so it's impossible to know if someone out there has an account
- The audio quality is total crap.
I use VOIP rarely (maybe once every month or so) so it's not a big deal for me. But SIP would be preferable to Skype. It's just not usable.