I've had BT Infinity now since April and am not very happy with the service.
Every evening I notice a great decrease in the quality of my connection. This generally happens between 6PM and 2AM. My ping to bbc.co.uk increases from a max of 31ms to 36ms (minimum being 29). I'm not that bothered about the small increase but packet loss also increases. I drop about one or two packet a minute.
What's most annoying is the dramatic speed drop. I go from 47Mb/s down to about 15Mb/s (sometimes it's worse than that and sometimes it's not as bad). However I should point out that my upload speed never seems to be affected.
I really regret leaving my stable ADSL connection with Sky and I couldn't go back now even if I could leave BT as they require you to take a phone package with broadband.
I strongly suspect this is caused by some part of BTs network being overloaded, if it is how long could it take before/if they sort it out (this has been happening to me for four months now). Also I live in Northern Ireland, could this have something to do with it?
Before 6PM: http://www.speedtest.net/result/2130084894.png
After 6PM: http://www.speedtest.net/result/2136669128.png