We got one of those not long ago too... when we bought it, we were planning on hacking it... but when we turned it on... it was just too cute!
I had some robotics people over to my house last weekend and were entertained by it for almost an hour... it's the most impressive toy I've ever seen. In fact, we forgot about him for a few minutes and were talking... then all of a sudden we realized he was gone. Right after we all got quiet looking around we hear him go "Whoa!" in classic WALL-E voice and come out from behind a chair. *chuckle* I love that thing.
It'll be fun to see where you take yours though. Good luck!
-q