What are the current bottlenecks in developing and applying CRISPR technologies?

I think of CRISPR as being a subset of "adaptive" bacterial systems that promote host survival. These adaptive systems are macromolecular systems that enhance host survival in a myriad of ways: by destroying foreign DNA, by mediating horizontal gene transfer, or even by altering host metabolism, among many other diverse functions. In this sense, CRISPR represents just the tip of the iceberg; there are likely many unexplored and uncharacterized adaptive systems that would be practically useful for genomic manipulation.