I agree with other commenters here: it just needs a bit more accessibility to make it perfect:
Ideally, allowing any app to route printing through it.
As far as I can see, the app is limited to the types of documents that it knows (pictures, some types of documents) and web pages --but then no perfect rendering of PDFs (sometimes a black slab will replace a background image, yuk!)
One way it offers around is to look for the printing history from other apps. But then it requires having been able to print from that app --maybe sometimes.
Documents from cloud services: Yes, if you are sticking to the main Dropbox, iCloud Drive, Evernote and onedrive. Woe to the users of alternate cloud services (pCloud a favorite, unknown to Brother iPrint as of today)
So, I love it for my pictures, and, hmmm. My pictures. Does the nitty gritty and I can always make screenshots, but no, no clean documents as yet.