You know, this is actually going to be a really interesting topic since we have a lot of writers here.
I'll withhold my ideology on the pairing fics for now, but for non-pairing centric (even if pairings are still present), what I like are the darker stories that show a bit of realism. In most magical girl shows, and fanfictions as well, the toll extracted of that lifestyle is just swept under the rug. Or if it is shown, it's brief and minimized. It may sound like a downer to want to see the darker side, but that brings about such gripping reading.