I have the DVD's and the gliding discs. I actually like the discs themselves better than the workouts (though Mindy's new "Gliding, beyond the basics" that's due to come out soon might be better).
I actually hadn't used my Gliding discs for quite a while until I went to a conference last month and at the last minute, decided to put them in my suitcase. Since then,, I've rediscovered them, and like to just do a few sets of a variety of 1-legged-squats-with-other-leg-moving moves! I also use them for push-ups, putting one hand on a disc and moving that hand out when I go down and in when I push up. Creates kind of a 'flye' effect on that arm.
I use my gliding discs with TLT workouts (they have quite a few "stabilize one leg while moving other around" moves in). I've also taken them on vacation and used them in my hotel room (highly packable, and they work wonderfully on hotel carpeting!).
What's nice about rear lunges using the Gliding discs is that the glute of the moving leg is engaged during the whole move, not just at the beginning and the end points.
I think they're great little workout accessories that are well worth the price.