I spent about 3-4 hours a week, including homework, with an extra 5ish before exams. I got an A both semesters 🙂
What no one else is mentioning is that it completely depends on your major. No, seriously.
Someone above mentioned that orgo is like learning a new language. It is. On the whole, those of us who were liberal arts majors did better than those who were/had been science/math majors. (This was a post-bacc.)
The hardest thing for people to grasp is that it's not like chem or physics; you can't just plug things into a formula and expect it to be right. There's often more than one way to approach things, and that's sometimes more confusing than the concepts themselves. If you're used to non-linear thinking and problem-solving, it'll be easier.
Shell out for a really nice model kit. Don't underestimate how helpful 3-D visuals are.