My faithful Logitech Cordless mouse became utterly and completely useless with this version. No button was any longer functional, not even the wheel. Even the speed was affected, as it slowed down to a crawl. No matter how much I'd fiddle with the settings, it didn't change a thing, so I uninstalled it and re-installed 10.4.8, which had served me well so far. Thankfully, the old version remembered all the settings and prefs, and the old mouse went on roaring all over again. Peccato, Alessandro.