i think someone else on here will explain this better than i can, but ignoring the glare issue for a moment, as stu said above the problem for me as someone who does print design, is that glossy displays produce colors that are only reproducible on other glossy displays. if the color gamut of a glossy display is:
...|--------------------------------|...
the gamut that can be printed is:
...........|----------------|...............
that makes working on such a display a huge issue. even the gamut on a matte display is still wider than what can be printed but the colors are represented in a way that more like how they print. having said all that i have learned to never fully rely on my calibrated monitors; i rely on a combination of pantone books, printer's Kodak proofs and the final press sheets to see what the color really looks like. a good calibrated monitor will only help you make a better guess.
...|--------------------------------|...
the gamut that can be printed is:
...........|----------------|...............
that makes working on such a display a huge issue. even the gamut on a matte display is still wider than what can be printed but the colors are represented in a way that more like how they print. having said all that i have learned to never fully rely on my calibrated monitors; i rely on a combination of pantone books, printer's Kodak proofs and the final press sheets to see what the color really looks like. a good calibrated monitor will only help you make a better guess.