Question on iMac 27 for pro photographers

I am posting this question here, because I dod't need just computer guy's opinion. I need to know true photgraphers' experience.

My concern regards iMac's screen. I heard that 27in iMac's monitor is too bright and too colorful to show real image's contrast, tonality, colors etc. I assume iMac's screen is adjustabile, however is it flexibile enough to match the reality and a lab's print? Please share your experience.

Thanks - Jack Cohn