It really depends on the student and the teacher. Some teachers are fantastic about putting everything that the student needs online. Links, reference books, calender formats with due dates on them, lesson after lesson, slide shows, etc. Then there are the horrible teachers I dispise that only put what the student needs to know online. I just want to yell at them, "Idiot, I'm here because I want to learn now will you give me something interesting that tells me you actually like your job instead of forced by the college to give an online class."
Then it depends on the students. Some are not cut out to study and learn on their own. For example, most students need an actual teacher there to help them understand math or english main points. Or they need to be forced to go online and actually study for a class they don't have to physically go to. Homeschoolers are great at online schools because they are used to it. Public schoolers have a bigger transformation to get used to.
One bad point is that sometimes you forget the class exists because you don't have to go anywhere. If you do take online classes, take more than one. It's less easy to forget about doing your homework at that point.