Yeah, some issues with SMETS2 fittings early on (though they did a lot of investigation into SMETS2 problems and identified a cause with the method of QC testing! which they blogged about). Apparently some trials with some customers getting decent customer service and meter-related stuff sorted.
I've personally never had an issue, but I've never needed a smart meter or any meter-related work doing. Tariff I'm on is fine, no exit penalties on their fixed terms. I've heard of billing issues for some people who've moved (or moved out). I've also read about some issues with getting service at very new builds.
Customer service seems to be suffering during lockdown1&2, fortunately I've not needed to talk to a human. In the past they've been very responsive and added me and SO on to the account with our emails so we both get account related info.
CS during lockdown has been a million times better than any of the Big 6, as CS were taken fully remote rather than downsized