At the time you get it Helm Cleaver is very good, but soon +5 weapons abound, and those with other advantages (e.g. stat enhancing) aren't rare. While +3 Strength is perhaps unique, there appear to be swathes of items that give +2 (at least two gloves for a start). Also HC is 2-handed which removes shield usage lowering your AC.
IOW it's good, but it's not to lose sleep over...
