Crazy RX Man has done a lot of posts on it - all negative.
http://crazyrxman.blogspot.com/
I can see why he's annoyed if it's "extremely tedious and time-consuming" to process the coupon, but that's inside baseball that's irrelevant to patients. For most of us with expensive chronic illnesses (I know you're familiar with those!) there will always be tedious, time-consuming administrative work involved in obtaining our meds. For my Crohn's and arthritis treatments there are copay assistance programs, shady benefits coordinators, and other middlemen that get dragged into these transactions every time my coverage or meds change, consuming hours of my time and theirs. Like the fragmentation concerns he mentions (which patients can take steps to minimize), it will keep getting worse until there's meaningful change to our healthcare system.
Privacy concerns also exist regardless of whether one uses GoodRx. He writes "Do you want your employer, or your insurance company, or anyone else to know you’re on anti-depressants, HIV medication, Viagra, or that you regularly get medication for genital warts?" Unless you've always paid for your prescriptions outside of insurance, your insurer already knows what you take and why you take it. GoodRx's privacy policy outlines what is and isn't shared so you can make your own decision on the value of your privacy. We used it for something perfectly boring and have divulged far more information about our lifestyle over the years by submitting grocery receipts to Ibotta and claiming Target Cartwheel discounts.
I forgot to mention earlier that when we picked up our prescription the pharmacist said to call them directly next time because they might be able to match an online discount without us having to sign up for anything. They didn't bother us telling that when we first called and they thought we might be willing to pay full freight. And that's how the market for a service like GoodRx is born. It shouldn't have to exist in the first place.