Well, I'm a graphic designer and bought a 2,8 ghz iMac and Adobe CS3 Design Standard this year, a Mac Pro and CS3 would have been too expensive.
At first I was sceptical about the glossy screen, but I was pleasantly surprised. I calibrated it just with the preferences tool and turned the brightness all the way down, and now it has very nice neutral greys and I'm pretty satisfied with its colors.
If the exact reproduction of certain colors is extremely important there is no way around a proof from the printer anyway. Otherwise there will always be a shift between screen and print colors, it also depends on other important factors like the paper something is printed on.