Prof Hansen\355s lectures can be boring, because he lectures straight out of the book, but he does cuss in class once in a while. His hw assignments were very easy and practical; you could learn something occasionally from it when you apply physics and math to astronomy for the problems. The midterm and final were straight-forward and easy, they were mostly conceptual questions, with maybe 1 or 2 calculations to conduct. Whenever he was in his office he was always down to chat or help me out. He is awesome, period.

Mixed feelings about him:
Lectures are very interesting, go at a good pace, and are always comprenensible. His midterm was pretty tough, for two reasons: one of which was the TA's fault, however. Problem was that he was not very clear about what he was going to test us on. So we get the test, and there is a problem about gravitational redshift on it. A problem which required the redshift formula, which I don't think anyone thought we needed to memorize.
Anyway, he was very lenient about it all and actually let our final count for 70% of the grade instead of the midterm for 30 and the final for 40 if it ended up helping us out.
For the final he was very clear what we were expected to know, so no problems there. It was actually one of the easiest tests I've taken.
Homeworks were always interesting, usually relevant, and usually challenging enough to get you thinking, but easy enough to be doable, though I can think of two problems that were just ridiculous.

It also bothered me that he never gave out a syllabus. He just wrote "Syllabus: follow the book" on the board the first day of class. Said nothing about what part of the book or what the homeworks would be like, or when exams would be, or when he had office hours. (though he was in his office very often)

Interestingly, I never bought the book, borrowed it from a friend twice, and never had any problems from that. Same was the case with Astro 81: the book is entirely optional.