Pass on the Peking Duck in Beijing unless you are a Peking Duck aficionado. I was in China this summer, my first, and I have to admit the food didn't do it for me in Beijing. Shanghai and Hong Kong were great. Don't get me wrong I love trying new things but Beijing was another story. Having said that, I did try the Peking Duck at I believe QuanJude (I don't know the exact way it's spelt so I'm using what other posters have used). I have to totally agree with jhm that they only have the reputation and it is in fact touristy and overpriced. As far as price, I think the English menus they have for non-Chinese are inflated, just my gut feeling.

Skip the duck in Beijing and get yourself to Shanghai or Hong Kong, so much great food! First, do the Great Wall before you leave!