You can grow just as potent of grass with CFL as any other light source. You take a hit in time and quantity and it isn't real efficient and can be cluttered. BUT, when you can grow a quarter lb every few months in a small box and your electricity bill only goes up 15 bucks, that is the kind of inefficiency and mess many of us can live with.
Long live CFL... people can debate the if and or but's, but it get's the job done.