On OSX ST2 b2188 (dunno about others) I find I can't redo after saving. (The console says 'unable to parse command' with keybinding (cmd+y) or actually using the Redo command from the Edit menu, so I assume it's not a plugin/keybinding clash.)
I regularly find myself testing code by switch between amended and non-amended versions of the same file by putting code in, saving, testing, undoing it all, testing, redoing it all (or some of it), testing, etc.
Is this a bug or intended behaviour? Maybe it's something specific to OSX (only recently properly switched so I don't know its idiosyncrasies).