The only problem with this format is that it is initially misleading for those who want to judge the series immediately upon watching a single episode, but as a whole the series is able to offer incredibly well-rounded entertainment as a result. Each season would start by introducing characters, engaging them in comedic situations, and later expanding upon the story in detail.
Generally, the way the series progresses is through Two high quality seasons do the series justice, with a third as of now currently in the making. All in all it is a show that in spite of (or maybe because of) how ecchi it is, it manages to be solidly entertaining in every important way you can imagine. Besides having a lot of fanservice, it is remarkable in terms of production quality, comedy, story, and character development. As an ecchi genre type show, it surpasses the vast majority of them in terms of almost everything imaginable.
Sora no Otoshimono is an incredibly remarkable series.