For my Genesis II I've always had a griddle on the left side and it has been used countless times but it was never big enough. I was recently to the point of just buying a dedicated griddle so I would have more room when I thought I'd check to see what Weber offered. To my surprise I found the full size griddle option for my Genesis II and it made my day. I love this thing. I've always been a Weber fan and I was very happy to find this option. 
The Griddle fits perfectly, takes up the entire surface, heats evenly, season's up really well and drains the grease in a convenient way! It's perfect! Thanks Weber!