I have never worked with photos, but overall the screen on the MBA is quite awful given current industry standards and if photo editing was my primary reason for buying a new laptop I'd never go with the MBA. If it's bad for me and I'm rather ignorant as far as photo-editing goes, then I imagine it must be for anyone who can actually tell two shades of red apart.
But, of course, let someone experienced contribute. I'm just letting my frustrations out 🙂