After sitting in front a of Retina, or High-DPI monitor for a while now I had concerns about how non-optimized images were displayed. From a photographers standpoint, you want to have your images shown the best way available.
For non Retina users, this it what how non-optimized images (or probably better said websites) look on a Retina screen:
Right now I am making a slow move towards a full optimized website. Starting with the blog section, which is Retina ready at the moment.
One note about Retina; once you are in, you never want to get back. Text, graphics, the overall experience, it is so much better. On-screen images on the other hand, i am not really convinced. Optimized imagery looks painstakingly sharp, very digital, very clinical. It has a huge influence on the look and feel of an image. I don’t know the exact figures, but given the fact that media consumption on the web is on the rise (and print is in decline), High-DPI monitors are probably the biggest change in how the viewer perceives photography since the transition from analogue to digital.