Vivid colors and images that pop - trademarks of the glossy screen. The matte images look too diffused and even a tad "soft" to me. And the glass is so much easier to keep clean vs. cleaning the actual LCD panel of a matte screen.
But you do get reflections - which I can live with.
+1
It is very easy to clean, and it's well protected. I didn't think about those before buying, but they are quite big advantages. The reflections are a pain in the butt though. I wish Apple would anti-reflection coat the glass, it would cost peanuts to do.