Glossy screens artificially boosts saturation and contrast giving a more pleasant but innacurate representation of graphics so they are bad for photo/video editing. For gaming, movies and casual use however, they look nicer.
I'm sorry but that is not true, it goes against physics and logic. In fact these panels show the true display output, since a glossy screen is just a clear panel of glass or what ever material. This means the light from the LCD will pass through largely unchanged, its like looking through a window. A pane of glass does not enhance contrast or saturation. It is in fast matt displays that alter the image you see as these will reduce contrast and saturation as the coating (a 'rough' surface in comparison to glossy) will scatter the light coming from the LCD. Hence why they give the illusion of "reducing" reflections, they are still there but just scattered (like looking through a steamed up window).
So in conclusion glossy screens give you the true picture whereas matt do not and the problem in most cases lies in the colour set up of the display.