Yup, seen it. I’m not a huge fan of anime (although I do like Miyazaki, and this was the same animation studio), but I thought it was good. As @sarahjane90 said, it is quite sad. I would definitely recommend it. But bring tissues.
The part that really broke me was when Setsuko asks Saita “why do fireflies die so young?” That scene left me an absolute mess. I made it through the rest of the movie with few tears, but it left me feeling very heavy and sad for a long time.
It’s not my favourite by Miyazaki. Porco Rosso, a significantly more light-hearted movie, is my personal favourite.