Excellent service: if they\'re not on the line, they phone back quickly and they\'re helpful. Upgrading and downgrading is a matter of an email. Superb speeds. I think it\'s worth paying that little bit extra rather than regretting using one of the other services.
UPDATE, one year on:
I stand by my previous opinion. Also, as I am about to do a lot abroad, I am cancelling my broadband so I can comment on their closure facilities. They have been very flexible and helpful. Once again, excellent.
UPDATE
My previous reviews of Vivaciti were in 2007 and 2008, after which I moved away. On both occasions, as you can see above, I was congratulatory.

Being a loyal person when reasonably possible, on my return, I went back to Vivaciti over autumn 2014 to autumn 2015. Unfortunately, they have slipped.

There have been quite a few slowdowns. I have found hq rather loathe to do much; everything is an effort to them and their answer is to
ask the subscriber to carry out a whole range of tests, none of which are collated or used to the best of my knowledge. When I gave notice, they asked me why and I explained it. Then, later, when I made sure that notice was given, the same person asked me again. The final, rather odd, thing was that they billed me extra (admittedly it was a small sum which they wouldn't follow up because it wasn't worth it), because I transferred a day before my contract was due to expire. Yes, a charge for using their services - services I had paid for in advance - a bit less! So presumably, had I moved rather earlier to another service, they would have surcharged me handsomely!
I tried to find out the logic behind it, but did not receive a logical answer, not that a logical answer was likely (charging extra for using a service less - sounds right doesn't it).

Sorry, but Vivaciti is now a service rendered begrudgingly. Their original selling point was 'you get what you pay for'. Sorry, but there are other 'premium' services that cost less
but would appear to be better. I'm now trying Uno and will review after a while.