I like it very much. I think it's got an 1800th - 1900th century feeling because it was very common here during that time period (usually as a nn for Christina). I think sisters named Stina, Kerstin and Lisa would be soooo cute.
But aren't Stina and Kerstin sort of the same name? Like English sisters named Lizzie and Beth?That's neat that it has an old-fashioned feel to it for you - I like that!