The amazing thing is that all of our fancy Internet phones and local cell phones all work together. The only thing which doesn't work, is Google Voice from our Android mobile phones. I've read Google Voice doesn't work that way. However, Google Voice works great from our computer. We just had a video call with adorable Caylie today! :)
I'm typing all this on a Mac Air, over a VPN, which is hosted on Amazon AWS/EC2. That way, if someone's sniffing our WiFi, we won't leak passwords... We are in the process of setting up an office here, with a combined printer/fax/scanner/copier, all over WiFi too. So far so good.