I wouldn't recommend it if your goal is simply to learn how to grow pot.
I would recommend it if you are thinking about a job in the industry (not as a necessary, but it could be helpful)
I've attended. To be honest, it was a good experience. I was already growing, and vending. I already had read the popular books. I guess I just wanted to know more. Cement some of the ideas, I don't know. Didn't learn tons about the act of growing. Lots of it was fairly basic. Some tricks here and there though. They do offer extra classes, for additional money, that promise to get more advanced and focus on just growing. I took the 13 week Basic and Advanced semester. I also went back for an additional class from Kyle Kushman on Vegan Organic Gardening.
I definitely learned quite a bit. Most was about things surrounding the cannabis community. Learned about some of the people, the history, etc.
The real benefits to me are: Graduating Oaksterdam has helped me with jobs in the industry. Helps some people take you a little more serious, especially if you are young. The biggest thing is networking. You get to meet some cool people, and make some connections. Some argue the networking is worth the price.
Worth it? Really is hard to say. I don't regret it, but have a hard time flat out recommending it to others, too. I guess, if you can afford it, and have the time, why not?