Pros: The entire process is pretty easy. Just remember that the Avis counter is now with Budget instead of the Avis counter.
Cons: Be careful about the insurance coverage through Kayak. That's not Avis' coverage but Kayak. If you have any problems, you have to go through Kayak not Avis. Luckily this didn't happen to us but it's good to know before spending the extra money.