Fast alone is not enough
Something the bunglers of Ofcom and DCMS have yet to understand is that a high bit rate is of itself not enough - low latency and high reliability are also very important.
Admittedly on the wider web, content delivery standards are outside the ISPs control, but that shouldn't prevent them having to have demanding standards that require:
1) good, reliable connections that don't fall over too often,
2) don't suffer regular slowdowns due to contention (ie lack of capacity planning),
3) a decent and stable low latency connection to the ISP's own servers, and
4) minimal or nil packet loss between the customer and the ISP's servers.
I know we could add a whole host of other tech detail, but I'm just looking from a customer perspective that the connection is there when you want it, delivers its full contracted performance, doesn't flail about with miserable ping (screwing up gaming, tele and video conferencing), and delivers the requested data without losing it.