I have taken a few online courses and haven't had any interviewers question me on this. I think they're perfectly fine as long as you don't take the core courses (Ochem, genetics, etc.) online if they are offered. All of my online classes have been English, humanities, or social behavior classes.
Pros: I like online classes because I get to work on the assignments at my own pace. And if the class is easy and the teacher posts assignments early, you can finish the class earlier in the semester and not have to worry about it. Plus, you have more time to focus on the important classes when finals roll around.
Cons: Most online classes require too many essays! Yuck. Also, for people who are not motivated, it'll be difficult to keep up with the assignments, the reading, the discussions, and other stuff required by the class and not fall behind.