I have been a trainer and trainee on the Prisim System. I really liked it. I think the interface from the instructor side was pretty simple and self-explanatory. I did not have the opportunity to utilize all of the functions (creating new and original scenarios), but the packaged scenarios are pretty universal.
From the trainee side, any system will only be as useful as the seriousness with which it is approached. Luckily, most of the people I worked with were able to get past the "video game" mentality that people seem to have at the onset of this type of training. Overall I think any training is good as long as it is done well. I think the structured format available in simulator systems helps to keep the training on track.
It is, of course, not a substitute for range time, but used in addition to range time it helps maintain weapon proficiency as well as improves people's ability to think on their feet.
I too used the flashlight and Airmunitions in the system. The shootback cannon is a useful training tool. Between the cannon and the camera attached to it, the instructor is able to better "convince" a trainee that the cover s/he thought he was behind was not being used all that effectively. I have seen some instructors go overboard on the cannon and shoot anything that moved. In my opinion, the cannon is best used when it is synced to the scenario (ie. when the suspect shoots, the cannon shoots).
The department I used to work with would run citizen academys through the sim and also periodically would run media through. Tigerdvr was right, it sort of sheds a whole new light on confrontations for people who may have never been exposed before.
WT