The experience I dislike goes like this: The server gives you the hand-held terminal and then stands watching you, tapping his/her foot impatiently, while you hurriedly verify the check, then calculate a tip amount under the server's scrutiny. I guess I'm a wimp. With the server's eyes on me, I feel the pressure to tip generously, no matter how poor the service or the overall experience.
By contrast, I find the traditional system, where the server would drop off the paper check for you to examine on your own time, to be private, un-rushed, and less prone to error.
After three decades of paying my restaurant checks without a POS terminal, I've never encountered any monkey business during the brief time the server is in possession of my credit card. Is "restaurant credit-card fraud" really a thing?