I haven't, but my wife did. My wife learned alot from the class. She was riding much better once she had taken the class than before. I would definitely recommend it for beginners. After that, get some experience under your belt, and then take some track classes like Devi said. ;D
I took the advanced rider course a couple of years ago. Got a group rate on it, and the insurance discount has more than made up for the cost. The class consisted mostly of a good review of the basics.
I have not officially taken the course......I have sat in on it (basic) a couple of times with other folks, just didn't ride in it. I think it's a good thing for new riders and I could probably benefit from taking the advanced when it comes around here next time. Of course, I probably have to take the basic first.
I'm currently in the prosess of becoming a "Rider Coach" for the MSF. I think its a great course, particularly for people who are new to riding and want to get their license. I dont know what its like anywhere else but here in Cali, if you are under 21 you have to take some sort of riding course before you can get your license, the nice thing though is that if you do, you dont have to take a rider test at the dmv.