I've had burgers at Lush, Kiosk, Blue Frog, Hooters, a donkeyburger at some place in wudaokou, McDonalds, BurgerKing in Xidan, New York Burger (in wu), the streetburgers in the barstreet (avoid!), Tun's babyburgers, Let's Burger and Fridays (if i forgot
any they're probably not worth mentioning.
The only true competition to Let's Burger, is the Fridays burgers with Jack & Daniels sause. But the winner is clearly Let's Burger :-) If you like burgers, do NOT miss this place.