The lectures are deceptively well-designed, with lots of (asynchronous) interaction. Try a course, you'll see what I mean.
The homework is a little more brain-stretching. It usually involves some code reading and intuition that was not served to you on a plate during the lecture. I have found them very valuable.
Often you are filling in some mostly-working code provided by the instructors. My only quibble is liberal use of globals, which violates some of my instincts about how their code works and causes me to spend more time hunting odd bugs than doing the actual content. On the bright side they usually provide some test harnesses so you're not dead in the water.
I've really enjoyed it so far. Signed up for Norvig and another one next time around.