I do not use QuickBooks [QB] in my practice.  None of my clients use QB.   

Do any of you have an educated guess as to how many PS users are also QB users?

Do any of you use the QB to PS data transfer protocol in your practice? 

Are all QB users tied so tightly into PS that it would be impossible for them to leave PS?  IF SO, how bad would the PS software need to become before they would leave PS for a rival software company?