I have had one, and they were rubbish.
Basically they didn't have a clue where they were going to put the meter, connect it to the electrics without drilling through my walls and how they were going to make it work in practice.
They also had no idea about the mobile reception and how bad it is round here (whether it is 4G or some dedicated utility network). Which is important for smart meters if they are to work properly in smart mode.
Basically I don't think they care if the meters work or not. Just that they can install them and get a tick from the government for saying they have done it.
I think smart meters are great in some areas. I would certainly have one if I thought it was going to work properly but I know it won't.
I also had the fibre to the house cold caller round the other day who was talking to me about how many "megabytes per second" I was going to get compared with the current service I have. Which is a load of rubbish since all broadband speeds are commonly measured and compared in megabits per second which is 8x slower.
Most of these cold callers have very little training or knowledge so DYOR and you'll be able to confuse the hell out of them in about 20 seconds.
The only reason they are employed is that it is harder to say no to a human being to their face than to say no ticking a box on the internet for most people.