I currently have a Mid 2011 27in iMac. I'm a web designer and programmer by trade, so I was thinking of possibly picking up a MBPr now that they've refreshed them. (Plus I have not-optimal eye sight and having a retina quality screen really helps my eyes from eye strain.) I'm looking into the 13in model as I have a Surface Pro 3 for Windows development and the 12in size is alright. Is there any reason to go up to 15in besides a bigger screen? I had a 15in Windows laptop a good 5-6 years ago and that thing was a brick so I'm wary of the larger size for a notebook. Also, if I was doing the 256GB option (I'd use the iMac for main music/video storage) is there any need to increase the processor or is it basically just benchmark increases unless you went full-hog for the 3.0GHz choice? I'd be bumping up to 16GB regardless. Also, IIRC if you have a Thunderbolt-to-Thunderbolt cable you can use the iMac as a secondary monitor?