Do search engine cloakers really generate lots of hits to your web site?
Are they okay to use with search engines such as google?

I don't think cloaking could be a good thing to do with any search engine.

For sure cloaking techniques can, if used properly, and it's not this easy, give good results. But you take great risk to end up banned or blacklisted by the search engines, as this is the worst thing one could do to trick them.
Not really because of the search engine themselves, as they cannot check all web-site, but because of your eventual challengers, that could spam report your web-site, and this is not good.

Cloaking can be compared to doping in sports, you can last some time without trouble, but how long ? And what if you loose all your "SEO medals" at once ?

Not something to do IMHO.

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cloaking is a bad idea, you will get punished by the search engines very fast

Cloaking is a black hat techniques. search engine can penalize you for the use of cloaking.