I completed my first build recently, having made a quadrotor. I built it from scratch, no kits involved, using Wii bits for the IMU and a LPC2103 for the brains running my own code. Weighing in at around 2.4kg it's not the lightest quadrotor around, but its motors are more than powerful enough. I've yet to test the maximum payload. Oh, and a custom shipping crate.
I did a writeup with lots of pictures and some flight videos here:
No GPS or anything fancy yet - one step at a time. :)