3 years 11 months i`ve now been with Virgin Media.
In fact it`s only been 3 years 11 months i`ve been using a computer & Internet so Virgin are the only BB providers i`ve ever actually had. We kept with them even after moving home back in late 2008.
We had some absolutely laughable billing & communication issues to start out with back in 2006 and some speed problems with the jump from 10Mb to the new(at the time) 20Mb. We also had one or three other little issues along the way but nothing too major. It was often just the communication that was the underlying problem.
I have of course done the hours & hours on the phone trying to just communicate with the poor sod on the other end and i did actually come close to sacking them(vm) on more than one occasion. Also came close to pishing myself with laughter on that phone too mind you although i never actually did that either.

When all`s said and done they`ve not been tooo bad in reality and i doubt any other provider could have done much better over that time. Some more home grown Call Centres would have helped with earlier frustrations no doubt.
We very rarely get any actual downtime though and with seven of us here at home there can be quite a lot of devices needing connected including Desktops, Laptops, Netbooks, PS3, Wii and DS/i`s so the connection can get a wee bit busy of an evening but nothing it dont cope with.