I found this map of established and reported incidences of Lyme disease in the U.S.--it's by the CDC.
DVBID: Tick Map | CDC Lyme Disease
It looks like Florida is covered up. I think I'd want something that keeps ticks from even biting after seeing that!! Also, I looked up Comfortis, and personally I think it would be a waste of money if you're already doing Frontline or something like that. It's a chewable tablet (similar to Interceptor's flavor tab that I think you said you were going to do for heartworms?) that kills Adult fleas only, and only after it's bitten your dog. They say "kills fleas before they can lay eggs". How products like this work is that once they bite the dog, the medicine that is secreted in the dog's natural oils sterilizes the flea. Eventually that particular flea will die without having reproduced, but any other fleas out there (not in the adult stage yet) will be fine until they mature into an adult and bite your dog. I think if you're using a product consistently that kills fleas (without them having to bite your dog first!) then there is no reason to spend money on what I consider to be an inferior product. If all the fleas are dead in my house, and all the fleas that get on my dog die, why would I need to be double protected with another medication that only does half of what the first one did? Maybe I'm wrong, but that's just my thoughts. I know your vet is making that recommendation to you, but I'd pass if I were you. I know a lot of people use a product similar to Comfortis, but to me it doesn't replace the need for the spray/drops since I don't want all of those fleas biting my dog in order for them to die, and like you mentioned, it doesn't do anything for ticks anyway. If anyone else has any thoughts, I'd love to hear them....maybe I'm missing something??