Just finished this whole series. It definitely had some redeeming qualities. I'm sure it'd hit a lot of people's checkboxes with its aliens, alien politics, androids, battle scenes, fanservice, romance, slice-of-life, and the near end of the Earth itself. It had a little bit of everything. It's also only 8 volumes long: A reasonable length for a manga series.
If you're interested in watching a battle android that looks like a cute girl wearing a maid uniform go back and forth between the slice-of-life moments of taking care of a teenage boy and battling other androids and aliens, this might be for you. Interspaced between all of that is the tension of knowing throughout the whole series that she has only a limited amount of time left before she no longer functions. And the books constantly remind you by telling you exactly how much of that time she has left at regular intervals.
Personally, the one part of the manga I hated (beyond the fanservice— which I never like but am capable of ignoring as long as it comes in reasonable doses) was the ending. I can't get into it without spoiling the whole thing, but I thought it was a disservice to the main character.