I got a little excited when I saw these sound cars in the catalog, but now I think I'm over it.
Realistic sound in locomotives is great. Of course, I love horn and bell sounds. Sometimes I run full loco sound and sometimes just the horn and bell. But the trains themselves make enough noise that I have second thoughts about adding these sound cars. Sure, the toy/model train sounds might not be "true to life" scale railroad sounds, but it is still wheels rolling on rails and clicking on rail joints... Plenty of sound. So much in fact that there are multiple threads on how to deaden layout sound.
Plus, I think there would have to be multiple sound cars throughout a train to get a full scale train sound effect. Even my short 8-10 car trains would probably need two sound cars to balance out the sound throughout the train.
I do like scale PS-1 boxcars, but I'm passing on these.