I have been with TalkTalk since it started and, pleased to say, have had no problem with their service. I pay around £20 per month for free broadband, free phone calls at any time including 0870 and 0845, international calls and landline.
My two daughters have been using talk talk for some time, no problems with phone or broadband.
The free 0845 and 0870 numbers can make a huge difference to the bills.
As an ex customer of Tiscali who were bought up by Talktalk I've had nothing but trouble. Double charging, constant automated phone messages, a helpline that puts you in touch with Cape Town, South Africa, an administration that does not know whether its coming or going, numerous head offices, and staff who never get to the root of your problem.
There are some good points outined by Hugh Spencer above.