I like that you can see everything at once in one place; it's easy to navigate through all your documents for any given time period if needed! There are some things about this system we don't love but they seem minor compared with how much better our business is now because there was no other way before (and still isn't).
We've been using flight docs since 2013 so far - haven't had an issue yet besides when new features were rolled out which took us awhile to figure them out/learn what each feature did / etc..