Being a really heavy user of Documents 6, the Files app is not quite there, but it's more integrated into the system. Documents properly integrates the Photos app and your Music app photos and music onto the "file system", something the Files app is missing dearly. However, the Files app is more coherent with the whole OS, like for example, you can dump files from Keynote or Pages right to-and-from the Files app, and feels more PC-like to use. The other thing is that you can access recents the Files App without actually opening it (with tap and hold in the dock), making it even easier to access Files.
The Files App needs to integrate Photos and Music libraries into its system.