The term "personalized medicine" is a buzzword. We've been targeting specific environmental things in specific people for a long time now. It turns out it is hard to get people to get in shape, control their blood pressure, and quit their bad habits. Genetics is as personal as it gets, so that has become the new holy grail.
Genetics offers the ability to identify new risk factors and improve understanding of the underlying disease. Many of the identified common and even rare variants in disease don't lead to therapies, but they do tell us about the pathobiology, which may in turn lead to new discoveries and/or therapies.
We would love to study gene-environment interactions, but there are major power issues when trying to do studies like this in sporadic, complex disease like heart disease, hypertension, stroke, and the like. We're still trying to develop large enough sample databases and robust analytic techniques that allow us to study the interplay between millions of genetic variants and the often difficult to quantify or report environmental exposures that may act in concert in additive or even multiplicative ways.