Palmbob, thank you for an excellent rundown on the latest in flea control.
I would like to add that, WHATEVER method the pet owner chooses, being consistent in applying it makes an enormous difference in its effectiveness. In other words, when the directions say to apply the topical once a month, use it every 30 days, not just when you happen to notice a flea on your animal.
Make a plan to control the insects, then follow the plan. You will get better results, spend less money, and not contribute to resistance. Yes, I know about this. Not long ago I was responsible for 300+ greyhounds on a farm in Florida. Parasite control was a full-time job, but we did pretty well, even in flea heaven.