I remember you sharing how you used different sizes of Circa - have you switched to something more generic? Just curious - I've been experimenting with Circa and like being able to move different pages around.
I still use Circa for my GTD system: NA and Project lists. I use the spiral notebooks for project notes, which can be quite extensive. None of the Circa pages fit quite what I wanted, while being substantially more expensive (even than custom printing). For this particular application, having a permanent binding with pre-numbered pages is an advantage, as is a rigid cover for writing without a desk.