Straddle strategy

Hi.

Does anyone successful trade options with straddle strategy? I have read (not yet tested) that volatilty prediction should be easier than actual price movement, plus you can always control your cost. (cost of call plus put)

Am i missing something. Can I lose more on single straddle than the costs of both options? Also are there any costs when the options actually executes?

So far i have only traded futures, but options seem interesting.

Thanks!