The phone is assembled and working. It can make and receive calls. It runs off battery power and charges by the USB port. The LCD and buttons control a basic user interface. It can scan wifi networks and connect to them. Assuming you have your SIP account settings entered correctly, after a short pause sound goes in the sound hole and different sound comes out the other sound hole.
This is the part where you can fill in the blanks about how the project is so revolutionary and will make all the fundamental functions of humanity easier, faster, stronger, and better. But really, it's pretty cool to hold a phone in your hand that you designed yourself.