I got an email last night letting me know that the android beta was available for me to try out.
It seems fine, although there wasn't a choice during install to let me choose Galaxy S 2 as my phone model so i'm not sure if i'm experiencing bugs or features of another phone.
Either way the call quality seems decent between an iPhone 4 and my android and i'll probably give it a few weeks before deciding if it should replace my default dialer.
One thing that I was surprised to see was that video calling is not supported. I was sure that the press release I read announcing viber for android said video calling was coming too but so far, nothing. I can't even find any solid reference to it other than viber doesn't do it.
*shrug*
Anyway, anyone else using it? What do you think? Has it replaced your default dialer?