[Horace]

TFT screens don't have an electron gun and the only place you'll find phosphorus is in the backlight.

The reason TFT's don't cause headaches is because the image is stable until changed where a CRT display is continually being refreshed, your eyes still pick up that continual change even if you don't actually "see" it. Look away from a CRT screen so you can only just see it in peripheral vision and you'll probably notice it. The lack of electromagnetic radiation from a TFT may also help with the headaches.
TFT displays are also cheaper to run, about a third of the cost of running a CRT, a major consideration considering current energy prices and environmental concerns.
They also look a damn sight nicer and are much easier to place, be it on a desk or wall or wherever.
I will never go back to using CRT's despite CRT's superior colour accuracy, the benefits I and others here have mentioned outway that single downside. I never noticed a difference in gaming except being able to play longer without getting tired eyes, so I don't count that as a negative :p.