For what it's worth- we've used Kenny 2 different times, and won't use him again. In Feb of 2012 he didn't have our golf cart waiting, as he'd promised the day before. And he also didn't return his phone messages until 2 days after we arrived. So we did finally get our cart 3 days late, and then he never offered to reimburse us even though we had paid for those 3 days.
Figured we'd give him one more try for this past Christmas. We actually reserved over a year before, to be sure we'd get what we needed, which was TWO carts that time. He totally botched our reservations- had the totally wrong dates down. After ENDLESS phone calls the week before our arrival, we at least managed to get 2 carts, but then he ended up taking them 3 days early. Again- no apology whatsoever.
I've decided the aggravation of dealing with him is no longer worth it- I'd rather pay Disney's high prices than worry if we'll even have a cart. I know you read good reports about Kenny on here, but during our vacation, we also talked to a lot of people who have had bad experiences with him. I think maybe he started out as a good thing ,but his business is kind of falling apart for some reason.... Just my opinion....