I've slept on one in the studio at BWV and one in a one bedroom at AKV - Jambo. They were o.k. for a pull out. I'm a small person so I didn't have any problems with the size and I don't really sleep well anywhere so it really didn't bother me.
They are similar at all the resorts, some are just newer than others. None are great. Fine for kids but not comfortable for an adult for more than a night or two IMO. DVC is supposed to be luxury accommodation and I don't consider sleeping on a hard fold down mattress luxury . Some people think the sleeper chairs are more comfortable, I've never tried it.
My son was just talking about how DVC pullout sofas were really comfortable. He has slept on SSR and OKW recently. My other son always like the pullout chairs.
Our daughter sleeps on the pull out all the time, she has not complained about them. She's slept on them at AKL (both Jambo and Kidani), BLT and Aulani.
Hopefully when DVC replaces the old sleeper sofa, that the person who makes the decision has to sleep on test sofas for at least a week and choose the best one. I have slept on comfortable sleeper sofas, and my wife has slept on a comfy one at a friends time share. There is no reason for them to not be comfy. I think their reasoning behind this is to push people into a 2 bedroom. I think all resorts should have a certain percentage with 2 queen beds and the rest a queen and a sleeper sofa. 2 queens is better for me. We do not spend much time in the room, but some people do and want more room that the sleeper sofa allows.