Talk Talk - pah!
I had Pipex Business Broadband in my office. Pipex got bought out by Tiscali (and the alarm bells started to tinkle a bit...), but service was still good, low contention, good speeds all day (I did a lot of work in the evening with no drop in quality). Then TalkTalk bought Tiscali and announced that they were upgrading our service to use their backhauls, etc... Being on a ADSL2 exchange at the time, not a 2+ I had a solid 8Mb, with a throughput of up to 6.8Mbit/s with Pipex pretty well all day. After TalkTalk's "upgrade", the day performance rarely exceeded 4.6Mbit, and the evening performance was typically 360Kbit/sec. What's more they insisted that they could upgrade me to their up-to-24Mbit service, even though our exchange wasn't due for upgrade to 21CN for 18 months. They tried to blame my line, the exchange, all sorts of things. In the end I asked them to leave my life and signed up with another business grade ISP, and as if by magic, my line performance is back to, and if not better than, how it was with Pipex. It took quite a few attempts to get rid of TalkTalk, from asking them to go, it took three months for them to acknowledge the fact and tell me that "in 30 days your service will terminate", and a further 90 days for it to actually happen! I think they've gone now.....
And as for 3 - I've been a customer of theirs since the day they launched, I am a "Founder", and never once have I had cause to complain. When I've had to call them, I've resolved everything with just one call. I think I've called them three times since March 2003. Compare that to o2, who I used for a business shared contract, we seem to be on the phone to them regularly! Though, they do, on the whole, sort stuff out well.