I've seen surprisingly few reports of actual experiences. I'll take that as a good sign since media and social media would be full of disaster stories if there were more.
For example, before EES started I was seeing things like "UK travellers should expect 'four-hour queues' as new EU border system comes into force"
https://www.itv.com/news/2025-10-11/...u-border-rules and I'm not seeing those stories after launch, although I could easily be missing something.