I have been using a notebook like this for a couple of weeks now. It's fantastic!
Normally I have four or five active notebooks at any one time.
One grid paper for weaving
One blank paper for brainstorming and mind-dumps
One lined paper for the same
One dot paper for planning and bullet journal
And then one notebook for whatever
project(s) I'm working on.
Keeping these notebooks sorted and accessible is a chore. Having one in my bag is fine, but three or five... or more. Too heavy.
I got an A5 sized notebook because that's the size I like to write. At the moment I have three notebooks (one for research, one for brainstorming and notes, one for recipes) and a copy of
Politics and the English Language by George Orwell. The individual notebooks are smaller than I usually use, having only 60-ish pages instead of the 200 plus pages the big notebooks have. But that's proving to be a good thing as my attention span is never quite up to filling a full-size notebook all the way.
I printed out and cut the paper for making my own insert, but it turns out my stapler won't reach that far. I'm wondering if I can use my sewing machine, but it's currently under a pile of seed starting supplies.