Originally Posted by The Lion

Don't use them. They're popularly referred to as 'cloaked pages', not search engine cloakers.

The post above describes their functionality nicely. But search engines such as Google know how to find them. And not only that, if your competition is worth their piss, they'll be looking for any reason they can for knocking you back down the ladder.

It's just business, friend. And it's dog-eat-dog. We all want the advantage. But employing cloaked pages is considered spamdexing, and you can be banned from SERPs if caught using them. Even though they're geared specifically for metacrawlers, they're viewed as visitor deception. And visitor deception is the number-one reason most spamdexing website get banned.

There's a great many other methods to help you compete. Use them instead, and use them better than your competion.

Good luck,
The Lion.