> completely different device
You can twist it how you like but it doesn't make a difference - it's a device that the PR suggests that it helps you save energy and costs. One device (Nest) lives up the dream and is great, the other (smart meters) is the opposite - but it could be a great device too if it would live up the original PR vision.
> enormous task of forescating power demand
Not really, the electrical power transformer stations that are physically located near your home already communicate about the power demand habits to the central power grid network. There is no technical reason to track every single house hold every 15min or every hour.
> provide real time data to the utility
Do you believe it's great that a washing machine is running during the night to save costs for the power company (and maybe you) but keeps you and your neighbors awake and you have to deal with wrinkled laundry in the morning?
One can save energy at home, but the biggest power consumers at home are devices that are used at specific times - and that time cannot be deferred to the night - except one wants to be the slave of his own devices. On the other side a lot of energy could be saved in industrial production by optimizing processes.
Next time one buys a device check the energy rating - but be smart and cautious as some very energy efficient rated devices like new electric kettles and vacuum cleaners consume less power by using less Watt which means physically it takes longer to boil the water or the vacuum cleaner is less efficient as the engine is less powerful and it takes longer to clean your home.
Far better for the environment is to install photovoltaic panels near your home yourself. Especially then an electric car makes a lot of sense.