I have a filly at my house owned by a friend of mine that is Half QH registered. She did it to verify sire and get her baby enrolled in the breeder incentives. Unfortunately, the registered mare the she bred, she was unable to get the previous owner to give up the papers and it turned into a mess.
I have a stallion registered with AQHA and ARHA. They didn't DNA or anything like that but they did require a copy of his papers and registration number. It was pretty easy but in my opinion, a waste of $75. Most of the shows in our area are full of horses/trainers that didn't quite make it in AQHA or NRHA rings for whatever reasons. That might just be our area though.