I have a Genesis E310 and I purchased a Weber Basket Rotisserie #9891, I love it.
I use it for quick high temp grilling when I don't have much time to watch the grill, I normally remove the CI grates and place a pan with broth to catch the drippings on top of the flavorizer bars. I have cooked whole chickens, leg of lamb and rumsteak (I think it's sirloin tip roast) with excellent results.
It was priced at $180, but it was 110v and they couldn't sell it and since the store manager knows my house is one of the few here that are wired 110v-220v he gave me a 50% discount to get rid of it, knowing they cost $60-$70 in the states makes me even feel better about it, thanks.
I hope that helps,