Though the answer varies with major and individual decisions on which classes you sign up for, I have found classes at Puget Sound to be exceptionally challenging, with only a few exceptions. My freshmen seminar classes were difficult, but my writing and rhetoric course, Rhetoric and National Identity (a communications course) inspired me to declare a minor in communications because I was in awe of everything one could learn from watching films made in the 20th century about war. It had a lot to do with the Professor Susan Owen, who is a wonderful professor and a critical film scholar and who I cannot recommend enough.
I have never had a professor (I have had 15 so far) who was not willing and easily accessible to meet outside of class to discuss coursework, a paper, or just planning my future course schedule or interests in general. This is remarkable for me to consider, but again I may just be lucky in my experience in the Politics and Government department.
My favorite class has been an Comparative Politics class, Iran and Israel, with Patrick O'Neil. Not just because of his vast knowledge of Iran (he occasionally strolls over the border and casually watches religious ceremonies in the streets of Tehran) or because of his dedication and support to his students (will pick up his phone and call to give one of his students a recommendation on the spot), but even more because of the feeling of community that emerged in the class throughout the semester. Prof O'Neil is known to be one of the toughest in the department, so students banded together to have long study sessions and group documents to facilitate studying that listed hundreds of terms from the semester available to students in the class. All of these elements created an ideal classroom experience.
My least favorite class has been one of the history of the Pacific Northwest, and it was the second of the freshman seminars "Scholarly and Creative Inquiry" and was titled "Ecotopia". It may have been that the class was a history class which is not necessarily my favorite subject that I found it frankly boring, or maybe because I didn't have many choices from which to pick since every freshman is required to take a Scholarly and Creative Inquiry course. But again, my other freshman seminar (the course with Susan Owen) definitely balanced out the experience, so again you never really know what you'll get with the freshman seminars.