I've had my MES 30 for about a year. On my first few smokes (briskets, shoulders, chuckies) I noticed that the meat was reaching final internal temperatures way too fast. they were powering through the expected temperature plateau where the collegen and connective tissue liquifies. Result? tough, dry meat.
I checked the calibration of the built-in temperature probe on the MES and found it was way off. It was reading low, so the controller was making the smoker much hotter than I desired. I checked the calibration by using another digital meat thermometer that I knew was correct. (I poked the comparison probe through a potato and set it on the grate at the same height as the MES probe). I ran the MES setpoint up and down comparing the two measurements as the smoker ran through two heating and cooling cycles. I then averaged the results and did a quick linear regression on the data.
I found that both the span (slope) and zero (intercept) of the calibration was bad. But I now can set the exact temperature I want on the grate by plugging the desired setpoint into the y = mx + b formula for a line (see, 8th grade Algebra does have real world applications).
I set my MES Temperature setpoint = (Desired Temperature * .898) + 5.8
So if I want 225 F in the smoker, I set the controller to 208 F. Now my smokes come out more like you'd expect 'low and slow' would.
FYI... here's the averaged and regressed data: