There have been negative comments about TT / CPW for over a year (mainly about them making internet slower for some types of use like sharing files).
Depends on whether you are mostly concerned about the voice calls or internet service. You might want to read the discussion boards (and compare ISPs for user satisfaction and speed) at Think Broadband before switching, also see the ratings at DSLzone.
I didn't go for a combined package / 'free' broadband because there have been comments about weeks to connect sometimes (if you're not paying for it, it's a 'bonus' and you are stuck because TalkTalk are not breaking any contract or charging for something they don't supply - as TalkTalk *are* supplying the voice calls service they *promise*, and the internet is a 'bonus', when available).
Sorry if that sounds too negative, but I've been following them on Think Broadband and Usenet newsgroup called uk.telecom.broadband - search for TalkTalk ADSL on google groups - http://groups.google.com/
I cannot comment as a user of TalkTalk internet, but hope the links will help you with other sources to find coments from those happy or unhappy with that ISP and others.
I'm using another ISP, shown near the bottom on the ratings at DSLzone, but have worked fine for me since I switched in May last year - in case anyone wonders, I use Eclipse.