You can make phone calls, send SMS messages, AND easily add your own customized functionality, right now!. (they would too, had they used Qtopia) Heck you can even use it as your primary phone. I have been using mine for almost a year now.
You can hack on applications all you want, because Qtopia is GPL, and will always remain GPL. As an open source developer for more than 5 years now, I just don't get the LGPL and why advocates of free, open source software keep using that license. Do you want more proprietary closed source or software that will always be free?
Back to the Greenphone, in phone bounce mode, you can use the modem from your desktop. You can ssh into the device and get a console. Play audio and video, using the highly optimized Helix libraries. And, if you are like me, you can write your own Shopping list and bar recipe applications to impress your friends and bartender.
We have created an SDK that runs in a virtual machine so you can develop from Windows or Mac. We have a simple script that builds the root filesystem (complete with the toolchain!). No having to install unstable and complicated distribution building tools that eat your hard disk space and make you want to poke your eyes out with a spork.
We have done so much work on Qtopia for the Greenphone, it would make your head spin and let the blue smoke out of your computer! We have a huge team of dedicated professional engineers, working night and day (Europe + Australia!) bringing you the best and easiest gui toolkit in the world to use (when we are not playing ping-pong or drinking beer).
Best of all, the Greenphone is an awesome shade of green and does not look like a hockey puck!
 Just so everyone knows, these are my personal opinions.