Agreed on the Quadrille/graph love. I, too, don’t use the lined versions for anything except grocery lists.
Love those Gfeller covers - I sprung for the Bellroy x Field Notes collab cover for mine, I’m considering ways to get it to replace my wallet, since it can hold nearly all the cards I need to carry on a given day and I’m not big on cash (well, I am a huge fan of it, but I seem to spend it more readily and thus despite really disliking digital currency, I use it almost exclusively). But it also fits nicely in my back pocket, with a Caran d’Ache neon orange pen in my wallet pocket.
But it’s either the folio in the back pocket or a bare Field Notes (cf. grocery lists). I also carry at least one in my work bag which holds random daily notes, people’s contact info, etc. and comes out for personal ideas that I don’t want to get my working time involved with.
I’ve got a Snowblind edition I use for my synth patches since it’s super easy to find amidst the black and red of my synths and bags.
Oh gods, I have an entire box full of unused ones (mostly special editions), but because I have so many I feel really free to give them away or just grab a new one for a new project or subject matter! I always keep one unopened 3-pack from the subscription set aside for “later”, and immediately open the other, so that I actually do use them and don’t keep them as curio items.