I have restrictions enabled, but all the individual settings are off. My reason? Simple, by setting the restriction passcode myself I make it impossible for anyone else to pick up my iPad and set it for me.
Since I'm the only user of the iPad, it's a completely theoretical precaution; but if there is a chance you'll ever leave your iPad in use by some other, unsupervised, person, you might want to consider this. They don't have to be malicious, just curious.
Of course, if you forget what passcode you set you'll be no better off than if they set it for you, and forgot.