Do you like barebones apps? IA Writer is really nice if minimalist just-get-words-down design works for you, and syncs with Dropbox. It also has a customised onscreen keyboard so you have access to punctuation right there instead of needing to switch between layouts. Plain Text is in the same vein and free, but not as polished and I don't think it has the improved keyboard. I used Notebooks for a while but had problems with losing what I'd written - not something I've heard other people encounter but not something I wanted to risk again once it'd caught me a couple of times.