I took psychology 401 (human interaction research) which was amazing...intensive case-studies, but amazing, a biology 300 class (entomology, very good, but the professor was rather crude so I dropped, with good grades though), psychology 370 (personality, very good) psychology 381 (BEST CLASS EVER!! Abnormal psych, VERY easy), psych 340 (cognition...taught by the named hardest professor at the university...dropped it twice due to intimidation), english 485 (metaphysical poetry, very good...chaucer era mainly, intensive but fantastic), psychology 485 (behavior modification...VERY hard...but good. It was being taught as a 585 class at the same time, so it was graduate level...)
I prefer upper division because I think the professors are happier to be teachings more intellectual things, and not dealing with immaturity as much.