Watching Lain and then Haibane Renmei a while back got me on a bit of a Yoshitoshi Abe kick. What I very quickly realized was that NieA Under 7 is nothing like Haibane Renmei, or really, any of Abe-sensei's other projects. I found out later that NieA was what they worked on after Lain finished, and it was supposed to be a kind of break from the dark and heavy themes found therein. Furthermore and unfortunately for me, I was only able to get a hold of the English dub, which has very likely tainted my opinion of NieA herself.
Story: It takes place in a small town in Japan, set in a future where aliens and humans both exist. Mayuko, a human, lives above a bathhouse; the alien NieA appears one day and moves in with her. The "main" storyline is that they're trying to save the bathhouse from shutting down, and the running gag is mainly that NieA is constantly eating an already-poor Mayuko's food or otherwise getting her into trouble. There are also some hints at uncovering details of the circumstances in which the aliens arrived in Japan/on Earth, but those world-building elements are ultimately discarded in favor of staging a significant fight between Mayuko and NieA to test the strength of their relationship. Episodic shows generally rate pretty low in my book, and this one was very average in terms of depth, complexity, and my level of tolerance for weak plots.
Sound: Don't watch the English dub. NieA's obnoxious and childishly smug tone of voice still rings in my head to this day.
Characters: None of them really show a huge amount of character development, and I found none of them particularly endearing. The aliens' personalities are somewhat flat, which contrasts with some of the show's themes about discrimination and stereotypes. Mayuko is, quite frankly, pathetic, and the other human characters are boring.
Overall: Average-ness all around, but mildly entertaining nonetheless. Watch it if you're an alien or Abe-sensei buff, or if you like very average, episodic comedies with an oh-so-light dusting of social commentary.