Sally is mostly famous as a historically important series than a cult or a well made series. It is basically the first anime ever made specifically for girls, since anything before it was robots and heroes for boys. So basically it is the first shojo anime even made… No wait, it is also the first mahou shojo anime too, since the core theme is girls transforming and the like. Practically, it is the grandmother of Sailor Moon, Pretty Cure, Madoka, and all the rest of the gang. It established most of the formula, such as the transformations, the fuzzy mascot animal companion, princesses from magical kingdoms, and non-violent magic attacks.
Of course there is no such thing as parthenogenesis and thus even Sally was in turn the child of an earlier show. It was inspired by the American live action sitcom Bewitched. I have seen that show too and the similarities are striking. It also has to do with witches living in a different world than humans and having to hide their secret when they stroll around.
… And yes, Harry Potter took ideas from that too.
The production values are expectably nothing exceptional today but they sure looked interesting back then since with magic anything could be transmutated to anything else. There are transformation sequences as well but because retro shows were pure and never fan catering, there was zero nude in them, although Sally was acting all too perky most of the times. An interesting quirk is how the show began as black and white and later one “magically” became color since the technology shifted rapidly.
Being a children’s series, the stories are simplistic and practically predictable with magic working as panacea. There is some story continuity but it is nothing much and the finale is just happening out of nowhere for the sake of bringing a simple closure to the story. The characters are also not developing in any significant way and even remain as caricatures all the way, such as the tomboy girl and the girly boy.
I can’t say it is worth watching anymore, since all following series in the genre practically took all the elements and shifted them further into more interesting formulas. It is by all means the basic blueprint of mahou shojo and nothing more to stand out from the rest.