All new MYW adult tickets require biometrics. For some odd reason, only some resort keys need it. My guess is some people get the UPH (no biometrics) and others just add on a MYW ticket to their package. If you get a chance (and have an extra minute or two), take a look in the reader. All it is is a reflective surface (bottom) and in the back is the series of cameras.
Once the fingers are lined up properly, the cameras take the picture and finds certain "points" to measure the structure of your fingers. It creates a long string of numbers then attempts to match it to the original number on the server from the first time you used it. If its the first time, it creates the number and stores it. This is why if it gets messed up the first time, it won't work again until it gets reset.
There are a few factors that can mess up the biometric readings. The system does allow for some variances, but if too many are different, it will set it off. If you wear rings, it may not work after the first time. My fiancee did her's the first time with her ring and it never worked again until I told her to remove the ring and have it reset. Also, the sun plays a role in it as well. If there is too much light, the picture will be messed up. The devices are set up to recalibrate every hour, but sometimes that's not enough. If the device realizes it needs to be calibrated, it will just stop working until you manually recalibrate it. This way, the ticket needs to be over-ridden and ask for ID.
Once people learn how to use it and get used to it, it won't be much of a bother to guests. I've always used it with my ID and it's like second nature now.
