I think KOR is a formatitive show for the romcom genre, and a 1980's anime staple. It ended up being one of my favorites from the decade, however, your mileage will vary vastly depending on how you feel about its episodic structure and tropes.
I, for one, feel the episodic structure works in portraying a day-by-day life of a teenager, and also worked better given the ESP hijinks. This is a TV series meant for syndication and re-runs, and its plot structure feels more like Western cartoons than a typical anime series does. For the first cour, each episode begins with a short monolouge by Kyosuke that gives the series some heart, and ends with a Polaroid still from the episode... It helps gives the series a nostalgic, "coming of age" vibe, even when the series was new in the late 80's.
Funny thing about the characters - My impression of the collective opinion is audiences love Madoka, want to punch Kyosuke, and would rather Hikaru just be quiet. To act like Madoka isn't the main draw to the show would be a lie. On this website, she currently has 202 "Hearts" and only 5 "Broken Hearts" - She's a cool character with a melancholic undertone, and has a great design. The only bad thing people have to say about her is she's *too* perfect. As for my opinion? I agree with the former, she's one of the most appealing characters of the genre.
On that note, I admittedly like Kyosuke more than the average viewer; I sympathize with why people don't like his indecisiveness, but I find his monologues earnest and I like his voice actor's work. Finally, with Hikaru, I also like her more than others do - her bubbly personality is a good foil to Madoka's cool nature. Seiji and Hatta (The perverted supporting characters) on the other hand can go take a hike.
Character designer Akemi Takada adds a well-needed Shojo touch to the original manga art. Original creator Izumi Matsumoto (RIP) was inspired by Gou Nagai's racy Harenchi Gakuen manga, and the American film "Fast Times at Ridgemont High". While I respect Matsumoto a lot, his mindset when illustrating a cover was more "How can I make this cool and sexy?" while Akemi Takada's was "How can I display the melancholy in Madoka's eyes?". (By the way, I paraphrased these from actual quotes from them)
The show's animation uses nice, bright colors; While mostly average, it occasionally dips into some sick well-animated moments. Look the series up on SakugaBooru to see what I mean! Particularly, the OP animation is on another level. On that note...
KOR's music is the other aspect everyone agrees is amazing. A lot of younger folk are discovering this series through its soundtrack, as many are part of the "City Pop" genre that is very popular on YouTube right now. As someone who loved the OST before I even knew what City Pop even was, I can see why it caught on with so many people.
Overall, my personal enjoyment for the series was a 10, but if I rate it more objectively, I'd land it at about an 8. A lot of what KOR did ended up being codified into tropes... tropes that many might feel are tired or outdated to modern viewers. But if you like what you see of the art style and music, I say give the series a chance.