I use my moleskine very simply. The front is my inbox, where I scribble down anything that I want to pick up on later. I also sometimes write ideas, short stories, shopping lists and such into my inbox area and mark the entry with a yellow post-it tab (I some stuck into my front cover). The tab reminds me to go back and reread it later, at which point I can decide whether it is worth copying somewhere more permanent.

I also use the back of the moleskine, rotated upside-down, as my calendar. I use half a page per day and copy my 'hard landscape' for the next week or two on Mondays.

Finally, I have all of my next action contexts on 3x5 cards stored in the little pocket. Ok, that means that I am not purely using the moleskine for GTD but I find index cards much more useful than pages. For a start, I can scan more than on index card at a time, depending on my location. For example, in the office I can have my computer, phone, and office contexts in front of me without having to flip pages.