I just checked their site. It seems to be a Skype clone. You could switch to Skype, which has the advantage of pretty wide market acceptance including third party hardware.
"Computer to computer calls are free on Zoippe and Skype - if you want to call from computer to landline/mobile both charge - Zoippe is cheaper"
Very good point. But I still see a couple of advantages with Skype:
- There is no Zoippe phone. If you buy one of the several Skype phones you don't need a computer.
- After having checked out the Zoippe website for a bit, I am not exactly filled with confidence. ;)