Has anyone actually gone for this and what is the performance like?
Yup,
I'm on the 500 package for £33 per month and love it.
The supplied router is OK but limited in Config so I'm using my own MikroTik hEX S and UBNT UniFi WiFi network.
I get around 360-410mbps on WiFi and 550mbps on Wired.
Never noticed any congestion. already on my street of around 40 homes at least 10 have signed up and installations only went live in May
Openreach must be worried about this. everyone i know who is in coverage will be switching as soon as their contracts are up