I've now got Superfast Broadband, some hours ahead of the promised time.
Well done, BT! No April Fooling there.
As measured on my Samsung Galaxy S5 mobile phone, using BT home Wi-Fi, I am getting speeds of about 37MB per second for downloads, and 9MB per second for uploads. The PC itself (connected using an Ethernet cable) is giving me almost exactly the same figures. I dare say - on past experience - that these Broadband speeds will become slightly less once things have settled down, but even so it'll still be pretty fast compared to what I had previously enjoyed on 'ordinary' Broadband - 10MB per second for downloads, and 0.7MB per second for uploads.
The main benefit to me will be when watching catch-up TV, using the BBC iPlayer on my tablet. No more hiccups in streaming. And, as previously explained, the entire new deal will cost me a little less than before. It's therefore something more for nothing more.
Beyond that, it hardly affects my life at present. (One day, especially if I buy a new TV - not a high priority - the Broadband speed may become very important indeed. But it'll be Ultrafast Broadband by then!)