The CalTrans corrects tracking very well (I got a 1-2 cents error in 6 octaves for my Pittsburg Taiga), increases the tuning range for modules that don't have a wide range by default, and corrects inaccurate CV outputs of controllers (like Keystep Pro) by quantizing them.
The only problem is that its calibration input seems to have a low sample rate and poor (or no) aliasing filtering. It is very sensitive to distortion and noise, so the signal must be quiet and filtered for calibration.
It's not obvious from the documentation, you expect to just plug in the cable and calibrate anything, but that's not the case with this module, I even thought my module didn't work.
Also, the CalTrans could be more useful if it used calibration input not only for calibration (you calibrate once and never use it after), e.g. for turning portamento on and off on the gate, but it doesn't.