Everybody loves pretty pictures. Retina display can make your pictures pop. But for everything there is a cost. What does retina cost you?
Mobile website design requires you to make difficult decisions ranging from implementation decisions, SEO impact, and user experience.
Web design can be a very difficult thing to learn for anyone that is coming from a print or graphic design background. The most difficult thing for them to get used to is that you absolutely cannot know what the end user is going to see.