We put my Grandmother in one when she had Alzheimer's when it came to the point that she couldn't take care of herself anymore and only when my Aunt had become too busy, but she hadn't lasted all that long there before she passed away. Same with my Grandfather a few years ago. He was really reluctant to be in one since he loved his independence but eventually relented and lasted several months before passing away.
Not all of them are equal. There was a lot of research involved in deciding where to put them. There are chains out there that are to be avoided that don't take care of its residents very well. I would be focusing on government run locations, which at least in Canada, have a higher quality of service and care.
As an aside, I did some volunteer work for the latter for awhile, and my job was to be the mailman and bring the mail to the residents. It was at the very least, an eye opener. One day, I was just doing my usual routine, knocked on one of the doors, no answer so I entered, and upon opening the door, the first thing I see was the TV (facing directly in view of the door) turned on and set to one of the porn channels, and it was on rather loud too. Rather ironically, just a few months before, I had seen that Curb Your Enthusiasm episode that dealt with Larry's father embarrassing him due to playing his porn on full blast in the retirement home, and it reminded me of that. It was an interesting experience