The field sobriety test is merely a way for police to make up signs of intoxication. It is a subjective test. If you're there you've already lost. At least in my state you can refuse it without losing your license.

I'm not a lawyer, but I view it as akin to speaking to police without a lawyer. It has no upside for me, therefore I refuse to do it. I do submit to chemical testing due to that being a requirement of my license (in my state the portable breathalyzer is not admissible in court so I'm fine with taking that too).