Perhaps the sweat and tears spent in Unit 1, and what you've learned there, paved the way for the easiness of Unit 2 :-)

I thought the homework was easier, but to actually understand the Kalman filter took me a long time.

I'm not sure about it.
The only thing I can confirm is that Thrun was great to simplify a difficult topic, such as Kalman filter, that way.

Kalman filters can be bit confusing...but all you need to do is think and study for 1-1.5 hours of what you learnt in lecture! And all of it becomes crystal clear!
I also found Unit 2 quite easy and including the homework(+ there was not much programming)!! :)

I actually found Unit 2 harder...but I don't think I had time to study as much.

For me , Unit 2 was easier than Unit 1, but Unit 3 is even easier than the previous two units. Let's wait for the homework....

It was mainly a struggle to get "going" with the Internet Explorer and Python too many versions problem(s). The homework answers still act strangely and I am not sure if it is the "Structure" or if I look at the answers with an Internet Explorer browser that makes me feel uncomfortable with this set up.
Not sure at this time if the way the automated grading works or the IE/Python problems still aren't ironed out...by the time the 3rd Homework is completed I will have it all figured out.

It was mainly a struggle to get "going" along with the Internet Explorer and Python too many versions problem(s). The homework answers still act strangely and I am not sure if it is the "Structure" or Internet Explorer browser that makes me feel uncomfortable with this set up.
Conclusion: I am just not sure at this time if the way the automated grading works or it is the IE/Python problems still not completely ironed out...by the time the 3rd Homework is completed I will have it all figured out.