I haven't been around the drug, but I've been around the users...
...and the ex-users. Meth-users description of cocaine: a decent laxative.
But really, you can mess up your life just fine with crack or heroin or alcohol. And meth users can be about as productive as the users of any drug, if they keep it under control. And they can give it up about as easily as other drug users.
At least, that's what they told me.