I'm glad that more people are discovering Archive of Our Own. There are a lot of writers who only post there, and I sometimes feel like I'm the only one leaving them reviews
Oh, and I recommend signing up for an account even if you only want to read fic, because Archive of Our Own allows writers to hide their fic so that it's only visible to signed-up readers, so if you're browsing it without an account, you're missing a lot of fics.
Seems some of the more edgier stories are on that site.
Yeah, there are no content restrictions on AO3, unlike fanfiction.net, so some writers post their explicit fic there and only the fanily friendly stuff on fanfiction.net.
(technically most of the mature stories on fanfiction.net are against that site's posting rules, and in danger of being deleted if the site moderators notice them)
edit to add:
Archive of Our Own actually has fanfic about many of Simon's characters:
Land of the Dead
The Devil Wears Prada