A little over a year ago I spent a bit of time out of work (cheers Campbell!) and, for want of something better to do I built a few quadcopters for a few mates (yes, I know I need to clean the deck).
This is one I made for myself. It's the least fancy of the lot - it has the KK 2.0 flight controller which is very basic - no proper altitude hold, no GPS, no return to base, and no other niceties to keep it in the air for you. In fact, I suspect it has a very effective ground detector built in, and it is also very fond of finding itself vertical speed brakes.
This is about as far as you can get from a DJI phantom - it's pure flying, and a bit of a bugger to do as well if you've not done it before, but on the other hand I built it myself, and I can upgrade it at will, far beyond off the shelf units, and at a far lower cost - this one was less than $300, including transmitter.
At some point, if I can be bothered, I'll get another flight controller that will do all the complicated stuff for me so I can use it as a proper camera platform and have it follow me around.
Anyone else fly/build quads? If not, and you're interested let me know and I'll message you a parts list to make your own.