Depends on the subject. My school just started offering one online course over the summer, so I decided to give it a shot. I actually ended up loving it.
It was a writing course and ended up working really well in the online format. Discussing readings in class can be really awkward sometimes (mostly because I'm the only one who consistently talks

), but the online discussions gave everyone the chance to gather their thoughts, pull passages from the readings, respond to everyone, etc. Then when we actually did our papers, getting feedback wasn't really any different than in a traditional writing course.
We also kept blogs and I ended up getting friendly with my professor through my blog posts; we eventually skyped a few times to discuss my papers, recommended music to each other, etc. I later visited his office on campus in the fall.
Overall a great experience! But I can see how it would be lame for subjects that require more in-depth lecturing.