I have used the Milori, the Sencore, the Smart III, and the OpticOne. I ended up purchasing the OpticOne at a time when I could have purchased ColorFacts for the same price. Let me say that they are all good systems and will give good results depending on the needs of the user. Smart III is very affordable and gives accurate results, but it takes a lot of time to do a calibration cycle (e.g., to take readings from 10 to 100 IRE). ColorFacts has an extensive web site and user group to provide support, it is very user friendly, and offers lots of options, but it is more expensive.
I like that OpticOne is really the brain-child of Cliff Plavin, and that gives him a lot of flexibility in quickly adding new features to the software. The latest release has an automated grayscale calibration routine that interfaces with the Sencore or Accupel generator. You touch one button, and it automatically steps through the IRE windows and takes readings. If you do a lot of calibrating, this is a great feature. If you don’t have a signal generator, Cliff has also done the same thing using the AviaPro DVD. You connect a cable from the DVD player to your computer and a sound tone automatically takes the reading and steps the DVD to the next IRE window. Cliff also added a new feature that makes it easy to do screen uniformity tests and to calculate contrast ratio. This is very nice and saves a lot of time. I also believe that the OpticOne does a better job at low IREs. In short, I have found Cliff to be very creative in coming up with ways to make calibrations easier, faster, more accurate, and more fun.
I don’t think you will go wrong with any of these systems, but study their particular features and determine which one best suits your needs. I’ve been very happy with the OpticOne and would buy it again in a second.