I use iCloud for Notes mostly. I like having my lists and observations handy on my phone, iPad, and Macbook. The new version is more useful now that you can add pictures, etc. I also a spreadsheet in Pages that I update daily. Haven't put any photos on iCloud yet, but will probably do a few that I am currently working on.
Pages, numbers, Keynotes, Office, Powerpoint, Excel & Pixalmator across my Macbook Pro, iPad Air 2 and 6S Plus. Since the Sept 9th keynote I upgraded to the 1TB storage for $9.99/Month with already 250GB+ already used. I do also have Notes which I have since created some drawings with my iPad Air 2/6S Plus with my Apex stylus.
I'm actually trying to figure out what iCloud storage is best used for too.
I pay $1/mo for the 50GB of iCloud photo storage. I'm testing out how it works becauSe I'd like to dump my entire 200GB library on there but so far I'm unimpressed with their Apple Photos app and implementation and will probably stick to Google Photos (better search, better features and unlimited photo and video storage)
In still going to pay $1/mo because I guess I can have iCloud backup (and that "storage is full" dialog is annoying as heck) but is really like to discover something practical to fill the other 40GB with.
Besides nasty tentacle laden hentai? Ahhh, just kidding... about the tentacles that is
Well, a bunch of Word/Excel documents... some HTML files... photos... the usual stuff I suppose... and some 10GB worth of PDF files that would look really nice on an iPad Pro since they're mostly formatted for letter/A4 size!
iCloud for backup and some Pages/Keynotes files
Dropbox for all documents, pictures, and short video clips
Box for screen captures and pictures from online
OneDrive for Office documents
Google Drive I haven't put there yet.