People making sweeping statements that a £50 cable performs like a £1 cable and that 'digitial is digital' are very ill informed.
This is not the case at all. People with experience in sound engineering, measurement electronics, data acquisition, etc. all understand the importance of good quality cabling.
The fact that a digital signal is composed of 1's and 0's makes it just as susceptible to signal to noise ratio and bandwidth problems to mention a few.
Why do you think a cd skips if you record it too fast? Yes that's right, information is missing. Why do you think you can hear noise or boomy bass on some recordings? Yes that's right, unwanted information has been added to the signal. The same loss or coloration of the signal can occur down a cable.
These are more tangible examples as they can be 'heard', specially if you have a good hifi set-up. The very same thing applies to video.
Now, a more appropriate statement would be that 90% will not appreciate the improvement in quality that a better cable brings. This is becaue they either don't know what to look for, or because in their application it does not matter. A clear example would be Joe Bloggs viewing dvd's, browsing the web and using the Office suite doesn't much care for accurate colour reproduction. However, if one is a graphic designer this would be paramount and the use of something like a Blue Eye Pro calibrator is fundamental to their work, as well as the impact of colour banding and uniformity of the image.
So much more useful and better advice is to say that you will most probably be fine with the cable that comes in the box of your TFT. Now, if you really need it, you can afford it, and you have a means of callibrating your monitor (a buddy with a BlueEyePro?) then I'd recommend you evaluate a good quality DVI cable, keep the length to a minimum and re-calibrate every year.
Regards,
Loko