iMac Retina 27 Display vs. NEC MultiSync P221W

[Rizzo]

I have been using an NEC MultiSync P221W display for editing photos in Lightroom for years. However, I recently purchased a new iMac Retina 27. Although I have not calibrated the iMac yet, I am curious how the iMac's display might compare to the NEC in post processing. I would really appreciate your thoughts. Thank you kindly.