Engadget reviews the Samsung Galaxy S5.

Getting down to brass tacks, how well does the thing actually work? It depends. I trained the GS5 to recognize both of my thumbs and my right index finger, since those are the three digits I use the most when waking up the phone. Over the course of several days, I made dozens of attempts with each finger and it only recognized me on the first try about half the time — and that’s a generous estimate. More often than not, I had to swipe my finger two or three times before it let me in; typing in a PIN code would’ve been more efficient. Worse, there were other times when the scanner wouldn’t recognize me at all, even as I adjusted my swipe speed, angle and finger pressure. And even when it works, there’s a small delay after you swipe before the phone accepts your print.

As for one-handed use, don’t even bother. It’s technically possible, but the odds of success are so low I have a better chance of seeing Narnia each time I open my closet. Normally, I hold the phone in my left hand and try to swipe the sensor with my left thumb; however, my thumb is at such an angle that the sensor simply can’t recognize it. Sometimes it’ll work if I push the phone up a little higher and try to position the thumb at a more shallow angle, but even then, it takes multiple attempts, and it’s so off-balance that I’ve come close to dropping the device several times. Apple’s sensor, on the other hand, has no problem picking up my fingerprint from any angle.

When TouchID was first announced, critics called it a gimmick. Yet when people saw how it simply works and removed the hassle of unlocking the phone, other companies started taking note and implemented fingerprint technology as well. But merely copying the idea of scanning the fingerprint is not enough. You need to do it in such a way that gives a great user experience and people actually want to use it.