Gary, I've found the frontline to be excellent for Jack & Sunny. We put it on them on Tuesday and there are literally dead fleas everywhere where they are just dropping off them. It works to kill all fleas within 24 hours and also helps with dermatitis from flea bites on them, and also ticks etc.
Sunny has stopped scratching so much, which I'm really pleased with. I'm definately sticking to it and not thinking of getting anything else at the moment.