I tend to use 1.1x or 1.2x speed depending on the speed of narrator. I usually listen to audiobooks while doing other things, mostly exercising/walking since i'm limited on time, so I haven't been switching back and forth much lately.

However, I do love the side effect that if I start with the audiobook and switch to text, I'll still read (or hear in my head, I guess) the text in the voices of the narrator and characters. This makes reading a physical/ebook more enjoyable for me. It's easier to get the mental movie going when I don't have to create the sounds myself, and I can focus on the visuals.