The only real problem that I had when I joined earlier in the year was the router they sent me first appeared to be for ADSL only - I made a quick call and told how to make it work on fibre, but the wireless range sucked.
Have to say though the lady at CS knew her stuff, was very friendly and even recommended a decent router if I was going to buy my own (which I was)
Have had no problems with speeds, if the speeds drop off then I just reboot the router and modem and off we go again at full speed
Not once have they moaned either about how much I've streamed and downloaded.
In August I brought down 725 gig !