Stellvia is possibly unique in being a Shojo Space Opera. The science, while being correct in almost every particular, takes a back seat to the relationships and romances between the students (and between a few of the teachers, but not between students and teachers). The main characters, and most of the secondary characters, have complex personalities; there are no stereotypes in the cast. And while there are plenty of situations where the characters have to act or risk everything, the consequences of those actions are not sugar-coated.
Recommended.