I'd say they're not better than any I've ever slept on. My parents stayed with us at BWV last year for a few days and slept on one. They survived it ok. The kids will do better, I'm sure. They don't get the aches and pains yet from bad mattresses.
One really good tip though... flip the mattress! My parents said it made a world of difference.
Our DD, 17, hurt her back 3 years ago and needs to sleep on a "real" bed, so DH and I slept on the sofa bed in our studio last March. We didn't have any complaints.
DD 11 and DS 7 have slept on the sleeper bed many times and never had a problem.
We have had problems trying to put both in the same bed.A queen sleeper is smaller than a standard queen bed.
We bring an areo bed, very easy to set up and easy to transport.