Are there any disadvantages to using elliptical trainers?

I would not call it disadvantage but a special consideration:

For some people with hip problems, be it a hip replacement or something like hip displasia, the fixed width between the foot pads can present a problem. You can see them turning their feet out and often extending over the pad perimeter. However, this comment does not apply to a majority of people with hip issues.

Similarly, if pepole are of particularly short stature, the elliptical trainer may not be a good choice.

These are the only cases where I found an elliptical trainer not to be a good option.