My experience with biometric, in general, has been spotty.
==== Short Review ====
In short, if you are looking for something you can use to securely keep a loaded firearm, yet still have quick access to a firearm for personal/home defense - this is NOT the product for you. Go with something that is not biometric. Also, this device is not going to stop a thief for more than a few minutes max.
If you are looking for something that you can use to store a gun that you use for leisure (you life does not depend on it) - there's simply not enough space, I dont believe that's what this device was intended for.
If you are looking to inconvenience a thief, stall a child's access, or use for travel - provided you can fiddle with the print scan for a few minutes, then this is just the product for you. Maybe you forget passwords and combinations easily and dont mind scanning your print several times - could be a good purchase...
==== Long Review ====
I had purchased this item because I wanted something to keep small kids away from my loaded handgun (used for home defense), and I wanted quicker access than the dial safe. I did not need a lot of space, just enough for the gun (springfield with a tactical light).
I received the item late August 2009. You push the "start" button which is the 1st of the 4 buttons. When the mvb500 has not been programed, pushing the button opens the device without scanning - no problem. I programmed the 2 admin prints - 2 second swipe, flat and firm, as the instructions state.
After programming the admin prints I noticed the device is very fussy. This is not unusual though - its something I've seen with other biometric devices (laptops). Swipe, deny, swipe deny, swipe deny... after about 45 seconds I am able to get the mvb500 opened.
To counter this "fussy" scanning, I continued to add my index finger print, over and over (stores up to ~128 prints. I would use different pressure, slightly different angle, and speed of swipe (2 second, 1 second, etc). I would also place the device at different elevations, on the floor, on the bed, on the dresser, etc. This technique actually works with laptops pretty well. To you, its the same print, but to the device is many different prints - thus improving your chances of a successful scan.
I also found that the device will get lazy - it will work pretty consistently 1st or second swipe, and then the next day it will forget who you are entirely - taking minutes sometimes to get in. So for about a week, I'd do a drill waking up , swipe-swipe-swipe-swipe-swipe-click. Once I got into the mvb500 I would add another print. Maybe your fingerprints change after a day <shrug>.
At the present I probably have 60 - 80 prints of my index finger stored in this device. I am able to get it to open after the 2nd or 3rd try.
Here's more on the intended service. If you are getting this device to give you quick access to a pistol or revolver - for self/home defense - this device is a very poor choice. You might as well keep the key close by ***** which I dont recommend if you have kids (They will find it, I promise) ****
-this is a different topic but I suggest that you look into safety and firearm awareness for your children if you have guns. They may not have access to your firearms but over 40% of Americans own a gun, one of your neighbors or the parents of a child's friend will have a gun - and you cannot control those guns, and I am of the opinion that it is better to teach your child than to keep them in the dark on something so serious.
Hope the review on this product, and the other advice included, is of use to you - be safe.