Pharmacogenomics is definitely the field that got me interested in pharmacy, so that's where I plan to do research when I am at UCSF. All the reasons for it being such an amazing field are listed above.
It will bring individualized medicine or genetically tailored medications to the general population, and definitely make good on why sequencing the human genome held such promise for future therapies. The guess work of prescribing (which beta blocker or any antihypertensive, or which antidepressant (possibly), etc.) could be lessened, allowing the pharmacist to make specific recommendations to physicians (if this responsbility falls on the pharmacist).
There is one good text I know of out there:
Pharmacogenomics: Social, Ethical, and Clinical Dimensions
by Mark A. Rothstein (Editor)
I briefly read through this for a paper I wrote this spring, it lays out the scope of the technology and its impact on clinical trails, drug discovery, and even economic impact by it significantly decreasing costs not only to specific patients but to the greater society. It also goes into the challenges that lay ahead.
Here's a clinical review of pharmacogenomics that goes into some detail and knowledge we already have:
http://bmj.bmjjournals.com/cgi/reprint/320/7240/987.pdf
Anyways, it gets me excited about the future when I read these possibilities.