I am actually building one as we speak. The planning of the procject is more or less done, I only have to order in the rest of the parts. Opposite to the AeroQuad project(ehich i have to say, is beautifully made) I am using 4 1000w motors, and 60A ESC's and 4 batteries. I've thought about blogging the project so if anyone know a good blog client for this, feel free to speak up.
If anyone is planning on doing something similar, send me a PM.
Once the hardware is done, the possibilities for programming are endless.
Once the 3dof(x2) IMU's arrive, I'll se if my kalman filter works as it shall. Exiting 
Daniel