PC Magazine has always liked the iMac but they really really like the retina iMac. They tested the base config with 8gb of memory and 2gb m290x and said it benchmarked pretty well with Photoshop. Even gaming was ok.
http://www.pcmag.com/article2/0,2817,2470667,00.asp
http://www.pcmag.com/article2/0,2817,2470667,00.asp