I got my Makey Makey a week ago (I preordered it really early on). I haven't connected it to my Pi yet, still trying to get some audio stuff figured out.
I've seen several - there were some musical bananas hooked up to a Pi and a Makey Makey at Maker Faire Bristol last weekend, and I think there's one in the Beet Box too. (We also have one in the office.)