Or just straight Google Talk. I am able to video chat from my Tab or my PC in the U.S. to my wife in the Middle East on her MacBook Air or her Touchpad with no problems. Real time and clear as day. Plus it works for non-video chat to Android phones which means, even though she has no phone service, we can text each other internationally over WIFI/3G.
Tango is good for people whose hardware supports video chat, but the software doesn't; it fills the software lack. That's going to be most devices without the latest Gingerbread or Honeycomb, which includes video chat in Google Talk. For example: the Galaxy Tab 7...no native video chat client. So while I have it on my 10.1 and Evo, my wife doesn't on her Tab 7...enter Tango to the rescue!