First of all, my work has a "time clock" thing where employees touch a pad and their print is recognized when they enter and exit. I registered my 6 prints three fingers on each hand, and i did it three times at the office, and when i go to the machine it can't read them. I have no fingerprints that are useful for this level of recognition.
BUT FAR MORE IMPORTANT, the fingerprint is the LEAST safe way of identifying a person. Ok for your computer, if you aren't likely to be the target of identity theft, if you have little money to steal or few important secrets to be uncovered. But note that it is a VERY SIMPLE matter, to take any random fingerprint from a glass or anything you touch (the outside of the computer itself), make a copy, and make a silicone cast of it that can be used on one of those fingerprint pads.
But unlike with the pin number of your credit card or atm card, if someone does manage to copy it, you can't go change your fingerprint the way you can change your pin number.
I have never tried to make such a copy myself, but i have it from someone who does this sort of casting for product design, and it is apparently not a complicated thing to do. So fine if you want to keep your kids out of your computer, or your coworkers so they don;t read your email, but be wary of relying on it when real security is necessary.