Dew and I had a short dialog on this topic a few days ago. To repeat my experience, certain generic versions of branded medications do not have same effect in me as branded version does. Consequently I pay more and use branded version. Lucky I can afford that extravagance currently.
I understand from others that an ANDA generic co. need only certify that the active ingredient is the same as that present in brand version. I do not know whether my understanding is correct or whether it derives from statute or FDA rule. Thus other ingredients in formulation may well be different. That confluence of factors may or may not result in different safety or efficacy in different individuals. That is not a good way to run a health care system IMO.