Glossy presents a brighter, sharper image.
Matte is more true-to-life color.
If color is important, get matte. If you want things to look nicer on your screen (but not necessarily other screens) get glossy. Glossy tends to attract more dust, but that might be just because it is easier to notice.
And a word of warning: no doubt many users will post that "the glare on the glossy is a BIG negative." I have a glossy screen, and use it in high-light environments on a daily basis (including outside) and the glare is not bad enough to make me think twice about getting the glossy over the matte. I really like the glossy screen.