The main drawback of rate control is the need for long term anticoagulation....every patient(and I mean every single one of them) loathes it. It determines what they eat, ladies inparticular can't stand the easy bruising on the arems and legs, the constant trips to the doctor for anticoagulation monitoring (blood tests). The risk of bleeding to death from a trivial fall. The necessity of hospital admission for several days before any invasive procedure to get off the coumadin and on heparin. The constant risk of stroke despite going along with all of the above. IF, and thats a big IF, the drug works(especially oral) and keeps patients in sinus rhythm its a blockbuster for that market segment. Why do you think people seek ablative procedures if just rate control was so great.