My inlaws use Tiscali and apart from 3hours downtime in 3years, they haave had no other problems, although it is a little slow.
Friends use Virgin and have had no problem.
My parents are with Orange, and when they were freeserve, - great no problems, Wanadoo, were fantastic, quick no downtime.
Orange = shocking, regular disconnects but quick.
I signed up for Sky TV and Broadband in the new year when i bought my new house.
Engineer could fine a line of signal for the TV due to huge trees, so had to cancel TV and broadband. and only today has my line become clear from LLU left by sky since 10th Jan.
My mate is on sky and only connects at 1mb and is paying for 16mb, although i can not comment on the connect speed as i never used it.