Some interesting observations.
There are some that have said that the fingerprint scanner is fast and works flawlessly, while other are complaining how bad it works. I pre-ordered an S10 (not the plus version) and took delivery of it on Mar 8th. Out of the box I was easily able to add my fingerprint to the phone, and it worked flawlessly unlocking the phone every time with minimal effort or pressure on the fingerprint scanner... and it was "fast" unlocking the phone and showing the apps screen. For those days that I had the S10 I was thinking to myself... I don't see why so many people are complaining about how inaccurate the fingerprint scanner is, or how slow it is because the fingerprint scanner on my S10 is working perfectly. Then mid week I decided I wanted a larger screen. So I went back to the phone store and upgraded to the S10+. Now I know exactly what everyone is complaining about.
The first time I tried to register my finger print I thought there was something wrong with the phone. It kept saying Press Harder, Press Harder, Press Harder. I thought I was going to bust the glass on the phone by pushing so hard. I thought to myself that I definitely did not have this problem registering my fingerprint and I never once got a "Press Harder" when trying to register my fingerprint on the S10... it was easy and seamless with very little pressure required.
I've had the S10+ for a few days now and in comparison to the S10 that I had previously... the fingerprint reader on this S10+ is absolutely horrible. I've even registered my finger 4 times into the phone to make sure I've captured all possible angles. I used the "check fingerprint" option to ensure it's seeing my fingerprint every time (which it does). Then I go to try and unlock the phone and it fails most times with Try Again, or Press Harder. I've removed and re-registered my finger again using all 4 of the fingerprint options, and I still get an extremely high failure rate. I've tried every which way to unlock the phone... doing it slowly, doing it quicky, pressing harder, pressing lightly but still get high failure rates regardless. It usually takes me several attempts each time to unlock my phone before it finally lets me in.
Another odd observation I've found. If I leave the phone laying on the counter for several minutes then pick it up and try to unlock the phone it's guaranteed to fail (multiple times). But interestingly... once I do finally successfully unlock the phone using the fingerprint scanner... if I immediately go and lock the phone again and then immediately go to try and unlock it again with the fingerprint reader... works every time and from different angles, and with variable pressure. All I need to do is a quick light tap and it unlocks the phone every time - no problem. Put the phone down and come back 5 minutes later and try again, and it fails letting me in and I get multiple Try Again or Press Harder.
So it's interesting that I have personally experienced both sides of the fingerprint scanner performance. I had a S10 for a few days which its fingerprint registration and scanner worked perfectly each time (in fact I only registered my finger once on the S10 and it worked unlocking the phone flawlessly after that), then I switched to the S10+ and have no end of grief with the fingerprint scanner. This is what we are starting to see being reported out there around the world... for some people the fingerprint scanner works flawlessly every time and is easy and fast to use with just a light quick touch. Others have no end of grief with the fingerprint scanner. Could it be because the S10 and the S10+ have slightly different builds or thickness of glass? Why is it that if I leave the phone sitting for several minutes and then try to unlock it, it's guaranteed to fail unlocking the phone, but once I successfully unlock it, then immediately lock it again, then immediately unlock it again right away, it works every time... even with just a light touch, and seems to unlock fast. Is it caching the previous successful fingerprint login in its cache memory for several seconds making the unlock process easier, faster and more seamless?
There are definitely some strange anomalies going on... fingerprint scanner works perfect and fast for some people (on some phones), and works horrible for others. (As a side note I have such a high failure rate of trying to login that I finally disabled the fingerprint scanner process today and went back to entering a PIN instead as I was getting way to frustrated with failed unlocks - No Match - No Match - Press Harder - Press Harder.