The Beatles used to play nickel strings on their acoustics. In general many people back in the 60s did that. I'm using this set on a very very stiff Takamine G series 12 strings. I've tried all sorts of strings and it was always too stiff. The action on that guitar is criminal. Then I've brought the guitar to my luthier together with these Retro nickel strings and he said I did something clever because the tension is more forgiving on these. Unfortunately the high G (10 gauge) broke immediately. So I swapped it for a 9 gauge, and it works all right. My 12 string guitar is just an impossible animal, high action, long scale, if it's even just playable now it's also thanks to these strings. I've tried lots of other sets on that Takamine (stuff that was way more expensive) and it was just not playable. Pity for the high G, maybe if they sold also a 9 gauge set it would be great. It may sound a bit thin for an acoustic, but lots of budget 12 string guitars are terribly tough to play. So an even lighter gauge could make sense just because of that.
Sound wise, I like them a lot. Warm, mellow attack, not a bombastick modern full sound. It's more of a soft, smooth tone