For some preliminary reading on how to choose a LCD monitor for photo editing, read this previous post.
It is “assumed” that apple LCDs are much better than others for photo editing. However, I read this which totally surprised me.
http://forums.appleinsider.com/showthread.php?threadid=74635
Looks like Apple uses TN panels in Macbook Pros, which sucks. Really sucks. If I have to buy a laptop for photo editing, the only one I would consider is the Macbook pro. I was surprised to read about TN panels there. [Caveat - the new LED backlit mac book pros might be different].
Apparently, the 17″ imacs also have TN panels [confirmed in http://www.flatpanels.dk], whereas the 20″ and 24″ iMacs have IPS or PVA panels [mostly anectodal evidence].
I really wish all LCD manufacturers specify the type of LCD panel in their specifications!