What I learned in my Coursera class
I'm learning all sorts of interesting things in the Coursera class that I'm taking now – like exactly how you could do attacks on both public-key and symmetric-key encryption using quantum computers. But some of the more interesting things that I've learned have been totally unrelated to the class. In particular, some of the random discussion on the message forum for the class has been very enlightening.
Now quantum mechanics is fairly math-heavy. In particular, it uses lots of linear algebra, and if you're not fairly comfortable with linear algebra you'll probably have a very hard time with the actual quantum mechanics. Some of the people in this class learned linear algebra in graduate school - lots of them have advanced degrees in electrical engineering, math or physics. But there are also people without a formal background in it, but who have managed to pick up enough to let them understand the quantum mechanics.
In fact, one student (from a relatively poor country) claims to have tought himself linear algebra by reading the Wikipedia page on it.
That shows me that this person is extremely motivated. And it seems that lots of the people without the advanced degrees in EE, math or physics are similarly motivated. So in addition to learning some interesting things about how we might one day be able to break public-key cryptosystems, I've actually gained a bit of optimism about the future from taking a class on quantum mechanics – people who are motivated enough to learn linear algebra from Wikipedia will definitely be up to any challenge that will come our way.