Hi Cathy,
Someone was very kind to lend me her gliding discs and DVD's so I could try them out before committing to a purchase. From my experience, and her's, here's what I've gathered regarding your questions.
Qu.1 Can you use those gliding discs on carpet?
Yes, the gliding discs are meant to be used on carpet (at least the purple ones I'm borrowing are). I think if you wanted to use discs on hard wood or another flat surface, you would need to purchase special hardwood gliding discs.
Qu.2 Can you use weights while you glide?
Possibly. I have found that some of the moves using the discs really challenge my balance as well. Using hand weights might make the balance issue even more pronounced. This could be remedied by using ankle or wrist weights vs. dumbells. I've only experimented with the discs. The woman who lent them to me said that the longer full body workout was killer on her lower body and fried the muscles just fine without using added weights.
Qu.3 How do others incorporate gliding into their workouts?
My personal opinion is that gliding could be used a as good lower body workout. It seems that a majority of the most effective moves really target the lower body. I could see using the discs alternately with heavy weights to challenge the lower body. The upper body really doesn't get hit very hard using the gliding discs (although some of the push up variations are quite hard, the other upper body parts like biceps and triceps don't get a thorough workout). There is a cardio routine that isn't all that advanced and might make for a lighter day workout or for a workout when you're not feeling so hot, am coming back from illness, etc.
HTH!
