the question remains. Exactly what will replacing millions of
existing meters with "smart meters" due to save energy, enable green
energy, etc?


its all of the above,

it's an ip based device,
-usage can be billed at minute by minute rates
-the meter can disconnect service remotely, non-payment, walking
blackouts etc
-the usage can be viewed realtime by a homeplug based display in the house.
-this display can be programmed to adjust smart thermostats and delay
high use appliances by using x-10 or homeplug modules. (water heater,
laundry, dish washer)
-software for your pc can do the same as the display.

the displays/controllers are available now, for around $200. some diy's
have demos for the displays and pc software where the meters are now
provisioned.

the utilities now have the means to bill about the same way airlines
price seats. and best of all, they let you make the choice. (you
decided to use those 80cent kwhs')

and we get the opportunity to pay an additional $5/mo for the next 11
years to pay for their upgrade. (there are also substantial stimulus
funds being paid to the same utilities for the same meter... as "smart
grid" funding.)

At least the rest of you will be on par with our Texas highest "power of
choice" electric rates in the US brought to us by Bush and Wood, just
before they packed off to DC some 9 years ago. beware of politicians
helpin' you out ;-)