Re: estimated net "benefit" of £5.7bn by 2020
This is where I'm confused too. I submit exact meter readings each month. I have had no estimated bills for over 10 years. I also have one of those digital display doodahs (one of those British Gas wireless things) that tell me exactly how much energy I'm consuming in real-time (electricity only) and how much the running total is for the day/week/month.
Apart from the fact that a smart meter would automatically submit my meter readings (as opposed to me taking the reading once a month and submitting it using an app, all of which takes < 5 minutes), I don't see any advantage to this. Not for me anyway.
OK, the thing can take a reading every few minutes if you so wish, giving you a much more granular view of your energy consumption and trends, but that's about it really. Oh, it would include Gas as well (I think) so that's a plus.