Crowley's essays on "the Herb Dangerous" provide a lot of insight onto the use of that herb as a tool, as well as Israel Regardie's essay "Roll Away the Stone" that further elaborates on Crowley's essays. Keep in mind that the "samples" Crowley used were exponentially weaker than what's available now and of a single variety.
Like I said, it's a tool to be used, and like any other tool, it's not useful for everything. A hammer can drive nails better than a pen, but is useless as a writing implement.