RGP contact lens wearers are reporting very little, if any, disadvantages to wearing those lenses. The most commonly reported is the initial comfort as they acclimate to a new lens or they're being fit for RGP lenses for the first time. And typically they do have a longer fitting process as those lenses are custom in that they follow the curvature of the cornea and sometimes it is trial and error as we find a lens that is comfortable for the patient.
Plenty of advantages are reported by patients. Because of the lens material it does allow for more oxygen to the eyes and so it is an overall healthier wear for the patient. The hard plastic material doesn't absorb water like a soft contact lens does and so it doesn't accumulate deposits as easily as a soft contact lens. Many patients will report that the optics are better in an RGP lens and this is because of the firm shape and the lens doesn't have to readjust when the patient blinks.