I've been with TalkTalk for 13 months, only had one problem that was sorted out without problem (see below).
Their download speed estimate was 10 - 14 mb, I get 20Mb line speed with a download speed of never less than 16Mb, even at peak times, and it's been very reliable.
That said, I have distant relatives who are also with TalkTalk and had some problems with it, and got the runaround from phone tech support. Eventually turned out to be a dying modem, but I discovered that, not their techs. Efforts to get a new free "goodwill" modem from retentions failed, so as a result they're probably moving to BT when the contract expires.
A lot of negativity towards TalkTalk seems to be from their support.
My TalkTalk fault shows them in a good light : earlier in the year, the line went dead. No voice, no ADSL. I got a friend, on a different exchange, to contact TalkTalk and log the fault. This worked ok, fault was cleared a few hours later.
Similar thing happened to the same friend, who asked me to report the fault for her. She's with Plusnet. I tried to do this, even having her customer number handy, but PlusNet wouldn't let me do it without the customer password as well!
So on that one, TalkTalk win!
Ian