Imagenthatnj, I bought two digitals and later, both went out of calibration. My new KA ovens did the same thing when they were new. You don't know they are out, just things start cooking slightly incorrectly. They go bad just a little. Finally, I put all four... two digitals, Taylor, and that yellow kind... in boiling water. The two with the glass tube were accurate. The two digitals were off. So I started again with the test and both digitals were off again, but now different numbers. Both were only off 7 to 10 degrees, but in European buttercreams and candy, this is fatal. I gave up and threw them away. Just be sure to periodically check them. One was the top rated CDN. I don't think I have a problem with digitals, it's just when they go slightly bad, you have no warning. That was when I started looking closely at pictures in my cookbooks, shows on Food Network, and youtube, and the majority have the Taylors.
For the ones that read the surface, in situations where temp is critical, and it usually is in sugar, a surface reading will not work. The Taylors have a stand on the bottom to keep them off the bottom for an accurate read.