As said earlier the case doesn't stack up for the user (avg. saving £12 per year I think). The real plus is on the generation side, where a Smart grid will make sure that the correct amount of power is generated at the right time instead of generating a load of electricity which doesn't get used, so it's better for the environment, innit.
Sounds like Cojack had a smets1 meter installed which reverts into a dumb terminal when you switch supplier (because these meters don't communicate with the DCC yet, they only send messages back to their suppliers). The govt. says that they'll have the capability to handle smets2 meters ...errm soon. Even so, a lot of the suppliers have a large stock of smets1 meters that they won't be returning but sticking on people's walls to make sure they reach their legal obligations. So I wouldn't be volunteering for a Smart meter until say early next year.