Biometric door locks?

Home fingerprint keypad lever locks seem cool but do they work? Are they more trouble than a regular door lock for home?
Would be great to hear from people who own one.
Update: The ones I've seen online and the home shows claim one year 4 AA bateries. No worry about outages.
Update 2: This is where I went...
http://www.keylessdepot.com/shops/index.php?main_page=index&cPath=28
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