I used regular printer paper to do a test of a mariner's star block. Then I got the paper piecing paper from Carol Doak and what a difference. It's thin paper, not quite tissue, but it holds up well and goes through the printer just fine. The regular paper one is so thick and bulky by comparison that I think I will do that first test one over on the thin stuff.
I also got some "paper" that feels and looks more like an interfacing at JoAnn's. I like it much better than the thin stuff, it has a stiffness to it, but it is expensive.