I had the same issue (2012, WP 3.4.2 !!). Possible solutions while this bug is around:
1) If you use firebug, [x]Disable Browser Cache in the Net panel helps.
I even had a very strange issue, that the cached editor-style briefly appears (in a css-filtered) Firebug net panel for a split second, than disappears again. Took screenshots to prove to myself.
2) A full browser cache clear helps. For whatever reason thereafter the issue did not reappear.
3) Lastly, my preferred advice, if you have to also make sure, i.e. your clients on staging or live server get your incremental improvements (w/o any annoying cache clearance advice):
Relocate the file and keep counting up:
// add_editor_style('editor-style-01.css'); bump for every deployment
Hacky, but reliable.