Your comments

oh beg pardon, it only gives that prompt when the file is unsaved and has been modified elsewhere - otherwise it just reloads the latest version silently.
certainly on Linux, one would normally just mount the SFTP folder so it can be used as though it were a local filesystem
I realise this may not necessarily be what you want for web development, where you don't want to publish the changes until you have tested them locally, but the uploading to an FTP site could be done as part of the project's build script instead? :)
Sublime Text already does notify about external changes made to open files (albeit with said modal message box)...
don't forget it would be awesome if it sync'd installed plugins too :-D