Digital is good, but I also like to have the old mechanical dial thermometers in my system. I run a PID controller with its thermocouple for my RIMS, but I appreciate having a double check with those mechanical dial thermometers. Every once in a while, the PID will go haywire and need a reset and I still have a backup that measures in a different way. The mechanical dial thermometers are very durable and provide relatively repeatable readings.
The other thing that is important is to calibrate your everyday thermometers and thermocouples using a accurate thermometer. Its also important to perform that thermometer calibrations in your typical mash temperature range (say around 150F). Although calibrating at 32F and 212F (@ sea level) is better than nothing, I have found many thermometers can be several degrees off their indicated mash temp when checked with an accurate standard. There are too many ways to screw up a calibration when using the ice water bath and boiling water checks.
I picked up a NIST standard mercury thermometer on Ebay that I pull out only when calibrating. I stick all my thermometers in an insulated cup filled with hot water (~150F) and compare each one to the NIST standard's reading and adjust as needed. The thing with a standard thermometer like this is that you'll need it only once or twice a year. Quite actually, this is the sort of thing that a club should buy and bring to your club meetings a couple of times a year to provide members with a good calibration for their thermometers.