Here is a quote from Ken Abram's home page;

"There is a method for fishing in tidal rivers that will teach you more in a short space of time than any other method. It is the use of droppers. You will learn more about fly selection through using droppers for one year than you can learn in any other way."

I've been using droppers regularly for a few years now. Not only in tidal flow but in the surf too. Early season last year, when there was a lot of small fish around, catching two dinks at a time was a good way to put a bend in the rod.
Sometimes you even catch a couple that aren't so small