TheVerge also had this to say.
https://www.theverge.com/2019/3/1/1...lus-android-phone-review-price-specs-features
"The other new thing that’s embedded in the screen is the fingerprint scanner, which has been moved from the back of the phone. The S10’s scanner is ultrasonic, which is supposed to be more reliable and harder to spoof than the optical in-screen fingerprint scanners we’ve seen on the OnePlus 6T and other phones. It even works if your finger is wet.
But it’s not as fast or reliable as the traditional, capacitive fingerprint scanner on the back of the S9. The target area for the reader is rather small (though the lockscreen will show you a diagram of where to place your finger) and I had to be very deliberate with my finger placement to get it to work.
Even then, I often had to try more than once before the S10 would unlock.
I’d just rather have a Face ID system that requires less work to use, or at the very least, an old-school fingerprint scanner on the back of the phone. The S10 does have a face unlock feature, but it’s just using the camera to look for your face and compare it to a previous image — there’s no 3D mapping or anything.
I was actually able to unlock the S10 with a video of my face played on another phone.
Samsung says it developed the ultrasonic scanner because feedback from customers said they wanted the fingerprint reader on the front of the phone, and this design allowed for more screen real estate than placing a capacitive sensor in a bezel below the screen. The S10 also lacks the iris scanning login option of older Galaxy models, which would have required more sensors than the new hole-punch screen design has room for. The company told me that it will continually adjust and optimize the face scanner’s performance leading up to the S10’s availability.
But here’s my feedback to Samsung: go copy Apple’s Face ID system.
It’s far easier and more reliable to use than the S10’s nifty-looking but ultimately disappointing in-screen fingerprint scanner."
I think once the device is in the hands of more users and they have had time to put it through its paces, reality will set in, and then you realise the S10 isn't all that this forum is evidently hyping it up to be.