Video chat is a big thing for me, since I live away from my family now. Currently we tend to only do it on special events like someones birthday. Removing the laptop as a requirement would be really nice.
It's interesting that for now it's WiFi only, but in time that will change with 4G for sure. Over 3G, it's only going to work on AT&T and T-Mobile here in the US, since it's still routing voice over the normal cellular network. Makes me wonder if this is another big reason the iPhone isn't on Verizon and Sprint. I'm sure Apple had this in development for a while.