I always have at least one notebook with me, and quite often have 2 or 3 with me. The one that's always with me is a pocket notebook and after trying Baron Fig, Moleskine, and a few types of Field Notes books, I've decided that the only notebook in my pocket is the Field Notes Expedition.
Why I choose the Expedition
None of the notebooks I tried were terrible. In fact I loved the tear out pages in the back of the Moleskine and Baron Fig notebooks. I often would be in a meeting and end up pulling a page out of the back of my notebook to give to the person across the table.
The failure of the other notebooks is that they weren't that single notebook I could take with me anywhere. They're fine around the city, but when I head out on a hike or snowshoe or backpacking trip I don't want to have to fish out my trip journal. I just want to keep using the same pocket notebook I'm already using.
With it's waterproof pages and cover the Field Notes Expedition fits this niche perfectly.
Writing on the Field Notes Expedition
The biggest draw back of the Field Notes Expedition is that you can't just use any pen with them. When I first got the Expedition I was using a Fisher Space Pen for my EDC pen. Unfortunately the ink they use in the space pen is entirely incompatible with the Expedition, especially for a lefty like me.
I actually found that many of the 'favourite' inks people recommend were terrible in the Expedition. After a bunch of purchasing of different inks to test I found that the Parker QUINKflow worked fine in the Expedition and still wrote well in my standard paper notebooks.
The other great option is a felt tipped permanent marker. I was using a standard Ultra Fine Sharpie for a while and never got any on my hand. I just don't like the felt tip so went back to the Parker QuickFlow and decided to deal with a bit of minor smudging and ink transfer to my hand.
Yes I entirely recommend the Field Notes Expedition. I've taken them on many an overnight trip and they've been soaked but have just kept on working. I keep at least one unopened pack on my shelf and when it gets opened I order 2 more to put back on the shelf so that I'm never out of my favourite pocket notebook.