By platform lock you mean OS vendor-lock (i.e. apple)? Because FS Notes stores all your notes in plain text files (which is why I use it - pointed to a Dropbox folder). Admittedly it has a weird way of naming the files (presumably so it can have the filesystem act as a more robust database that is then loaded and cached) but it's still the easiest and most "free feeling" workflow that I've been able to stick with for my workflow (what appeals to me about FSNotes is: Plain text files, Syncs with Dropbox, Fast and simple keyboard shortcuts, Works on mobile and desktop, Quick and simple to organise stuff in folders but no tags or complex structures, Very cheap)