I've been using expandrive for the past year (and just upgraded to v3) and the sftp support is the fastest that I've tried. It caches what the directory structure looks like so browsing is quick. Opening and saving files takes about 1-2 seconds on average. Sometimes directories will get stale if I create something on the server, but hitting F5 or refreshing the directory fixes it pretty quickly.
I use it with ST2 for my editor, directly saving onto my remote dev box, and it works fairly well. My biggest hangup is actually with ST2 - I can't individually refresh project sub-directories, only the main one, and saving files in ST2 is a blocking operation -- can't do anything else, and when a save takes a couple of seconds, it can get frustrating. I've tried the SFTP plugin for ST2 and I still prefer this route.
I've had exactly your experience (expandrive, ST2, SFTP plugin) on OSX and I've also arrived at the same solution. Works well enough, but as you said, ST2's lack of auto refreshing of directories is a bit troublesome. Furthermore I've had situations where Expandrive wouldn't refresh either and I had to unmount/mount again - improvements in that regard is what I'd be looking for most in an update.
I use it with ST2 for my editor, directly saving onto my remote dev box, and it works fairly well. My biggest hangup is actually with ST2 - I can't individually refresh project sub-directories, only the main one, and saving files in ST2 is a blocking operation -- can't do anything else, and when a save takes a couple of seconds, it can get frustrating. I've tried the SFTP plugin for ST2 and I still prefer this route.