I use Facetime and Skype all the time.
My wife has my previous iPhone 4 (32GB) and I have a new 4S (32GB) and we have two kids.
Due to my work hours my oldest has to go to sleep when I'm not there often so my wife constantly calls me up and depending if I'm on WiFi or not we'll Skype or Facetime. We prefer Facetime as it's a bit better experience, but both work.
We also use it daily, in addition, when my wife is at work so my daughter can video call her and tell her about her school day (she's in Kindergarten so she loves telling us about what she did).
I admit, though, if I didn't have kids I probably wouldn't use it as often.