I’ve taken almost 20 online classes from two different schools and for the most part have been happy with them. They are not for everyone though. It depends a lot on how you learn. Some people are visual learners and it works pretty well for them, as you’re just reading the text book, etc. Some aural and kinetic learners have a harder time as you don’t hear the teacher lecturing, don’t get much hands-on experience, etc.
You are definitely on your own for the most part. The teachers have very little involvement with you and any that they do have is just through email. If you can’t figure something out from the text book you can email them or call them during office hours, but I’ve always just gone online to figure things out on my own.
And that’s another thing, if you aren’t used to teaching yourself things you may have a difficult time. For instance I was homeschooled most of my younger life and taught myself to learn computers, program, make web sites, etc so I’m very used to just reading information and figuring it out on my own. Others may require more direct interaction with a teacher so that they can ask questions and get immediate feedback, etc.
Many of the teachers that teach the online classes seem to do them as an extra part-time job. A lot of them work in the industry or teach traditional in-person classes at a university and then do the online classes in their free time. This means it can take a day or two to hear back from them and they are usually pretty brief with responses. A lot of times I feel like I’m an afterthought to them, or like it’s a hassle to interact with the online students. So like I said, you really have to be able to just read the textbook, do the assignments that the teacher gives you (usually just example questions out of the book) and keep track of your own time schedule and stuff to make sure things aren’t late.
If you can handle it, it’s great as you don’t have to waste time sitting in class, driving there, meeting their schedules, listening to lectures, etc. However some people need/want that and want the more social experience of school. I personally just want to finish it as quickly and easily as I can so I can get that piece of paper and move on.