I use them, but in a class each week.
I've found th a great high impact cardio workout, which also offers some resistance training, more a body tone than sculpture thing.
My advice on using them, though, is to go to some classes or get a DVD or some such thing, as although the diagrams/picture shots of the types of exercises you could be doing are great to inform you of just that, I have found though using them is more about technique than brute force.
Going to a class once a week is a great way to get the technique right and new ideas on how to keep it fresh and then you could use yours when at home another couple of times in the week.