One could argue the same thing about a traditional college degree. You spend a ton of money, take four years out of your life, and are forced to take a bunch of classes that don't even pertain to your major (breadth requirements).

At least with Khan, it is free, it can be done in your spare time, and you only focus on things that actually interest you.

Why would it have to be life changing in order to be useful?

The trade-off could well be watching soaps vs re-doing your high school or university level math.

I meant useful or lifechanging as two seperate questions -- no correlation.