You know, having used biometrics myself, I'm not sure that there really is any benefit from a security standpoint, at least personally.
There have been several examples of criminals even removing others fingers to gain entry to locations with biometric scanning.
As with most technology...the newer it is, the more flaws it has; the more vulnerabilities it has. I would, at this point, still consider biometric security a relatively new technology, as it is not universally deployed at this point. With that being said, I'm certain it has its flaws, and now, is more of a convenience than a solidified method to secure a system. But this is changing...as security vendors begin creating and marketing newer technologies (like fingerprint scanners that know if the finger is dead or alive), or that can determine authentic biological material (as opposed to latext overlays), the technology is going to be far more reliable and secure than passwords. On the other hand, you have eye-scanning, facial recognition, and voice recognition. You've seen the movies like James Bond, or Mission Impossible...so you know that with enough effort and resources, these methods become less secure...then again, as the technology grows, synthetic materials will be able to be determined from scanning and ruled out.
Conversely, biometrics systems are far more reliable in ensuring <i>who</i> uses it, as anyone can take a smart card or USB token.
<a href="http://www.itsecurity.com/features/biometrics-security-081108/">Check out this article.</a>
Hope this helps!