I was given a tutorial on one the other day, I like it and can see how it is good, the trainer i had said he only tends to push people to use it for strenthing your core.
They have a few in our gym that you can use, but they also offer courses.
Have you seen or tried the Vipr? Now thats a brilliant invension! Its a weighted tube which you use as part of a work out, I also had a tutorial on that and WOW!
The trainer said that he reccomends the Vipr over the power plates especially for Toning.
Do they do classes at your gym? I've been to body pump and that was really good! You could also try Body combat thats suppose to be good as well!