I've never taken an actual "online" course, but for a few of my one-credit IS classes, I never went to class and did all the work from the work books. These were classes like Word, Excel, PowerPoint, Access, Macromedia Dreamweaver, etc. I already had a basic knowledge of the software and had it all installed on my computer, so I did all the work at home and submitted it directly to the grader and just showed up when/if there was a test or exam. Most of the IS profs don't mind if you do this b/c in general, the people that are totally new to the software and need help will go to class and get the help.
I'm able to fit normal lectures into my work schedule, but I can see where it would be a plus to do some online. Like ylime said, to me they sound like more work b/c you don't have the Prof's insight or classmates insight immediately available and have to transcribe everything into your own level of understanding. I'm the type of student that can do really well just be going to class, paying attention, and taking my notes. A hate studying and going over everything again on the side, so I'd probably suck at online stuff.