I'm not sure if you're asking about the use of those specific literals or about the extensible reader, but there was a short interview with Rich Hickey about the new extensible reader and there was valuable discussion on HN about it:
So I'm hoping for someone more knowledgeable than me chiming in and explaining possible drivers/motivations for these literals. When do you write a literal uuid?
I assume that these extensible literals will be ported to the JavaScript and .NET implementations of Clojure, making it easier to work with rich data types without having to pepper your code with calls to date parsing functions, etc.
Having an intuitive, idiomatic concept of 'data' at the heart of your code is an important aspect of Clojure.
In comparison, I find it hard to the answer the question, "How is data represented in Java?" Which is why I find doing things like data transformation to be far easier in Clojure than in Java.