Energy smart meters: Great tech or a pain in the neck?

Over 26 million smart meters have been installed across England, Scotland and Wales. They come with in-home displays showing you information about your energy usage in real time, so can help you identify where you can cut back – especially important right now. Plus they automatically send meter readings to your supplier as often as every half hour, so you don't have to. Yet they're not without issues – for example, older models may go 'dumb' if you switch provider. So what's your opinion of them?