I have 2 Thermopens, one for poultry (yellow) and one for beef and pork (red).
I have had them for two years without any problems of any type. I use the Thermopen rather than total reliance on twist and touch. I like to know just how close I am to target time for scheduled dinner time, this allows me to adjust the cooker to meet my time schedule.
They are indispensable when cooking hundreds of pieces of chicken or 20 to 40 Pork Butts to make sure a safe temperature is reached before putting in the trays to rest. It also allows you to move items around in the cooker to balance out the hot spots.
If you keep an eye out you can get a Thermopen on an Open Box Sale with full warranty. http://www.thermoworks.com/products/..._box_sale.html
Everyone has their own method of checking, and bottom line is that there are differences in the same cuts of meat, so the thermometer is just a guide to assist you, except in the case of poultry. With poultry nothing leaves my cookers until proper temperatures are achieved in each piece of meat.