global-auto-revert-mode sometimes doesn't revert my buffers. These are regular files (source code), and this happens most often when messing around in source control (e.g. stashing changes, rolling back to an earlier version, the updating and un-stashing).
Edit: After further investigation, emacs v. 24.5 is using libgio to get notifications of file changes, but some notifications are getting dropped: file-notify-callback isn't called for some of my files. Perhaps a buffer somewhere is overflowing when so many files are changed at once?