I took the UC Berkeley Extension School online intro to human physiology course.
Overall, it was ok. Physiology is a class where I think a lab component would definitely be helpful (and interesting). However, scheduling constraints (and the fact that I just never got around to taking physio in undergrad) led me to an online course.
Pros: it was a pretty easy A. All of the worksheets and "review quizzes" were open-book. Only the final had to be proctored, which wasn't too difficult to arrange and the final was much easier than I expected it to be. The professor got your worksheet grades back to you quickly. I never contacted the prof with specific questions but he seemed like he would have been good about responding.
Cons: I got the feeling that the worksheets weren't very well constructed or proof-read. A lot of the wording was kind of confusing, there were answers that I could not find in the assigned textbook and had to look elsewhere for or were minute details that seemed rather trivial in the context of the chapter. A couple times there were repeated questions or matching problems where there really was no logical answer. There wasn't any real feedback on how you did, I just got an overall letter grade for each assignment (no percentage or point value) so I had no idea how many questions I actually got wrong and right, which was frustrating for me because I know I couldn't have possibly gotten every question perfectly correct.
Something that could be good or bad for you is that the course was self-paced. You start it and then you have six months to finish. Also, I remember some threads talking about how not all of the vet schools will accept this as fulfilling their physiology requirement (Oregon State doesn't have a problem with it) so that would be something you would want to look into before starting any online course. Feel free to PM me if you want any more specific info on the course.