Philip,
   You're right- the ES doesn't "require" an AOA.  It also doesn't require a
GPS, an ILS receiver, an autopilot, a multi function display, or a  whole
host of other things which most builders install.
   Having these things enhances our capabilities and/or awareness.  If you
understood the value of an AOA, you'd have installed one.  Sure your plane
will fly fine without one, but as I've said repeatedly, it's a great tool to
have in your box if you should ever need it.
  On top of giving me stall warnings, if my engine should ever fail
(especially on takeoff) I'll be flying my AOA all the way back to terra
firma.   There is one optimum AOA for all weights.  The same can't be said
for airspeed.  Do you know what speed to glide at whether you're by yourself
and light on fuel versus 4 pax and max gross?  Do you know how tightly you
can turn back to the field before entering an accelerated stall?  AOA tells
us that.  It allows you to manage and optimize your available energy in a
way that an airspeed indicator (or even two airspeed indicators like you
have) simply cannot duplicate.
   Fly safe,
  Skip Slater