I use them when I train my clients and teach classes. They work better on carpet. They are great tools to incorporate in your classes. Use your judgment as to which clients are able to safely use them…not for use when balance and stability issues or a weak core are a concern. The gliders used for moving furniture are cheaper and as effective as those sold in fitness stores or online, and you can buy a package with several pairs in it for under $10. Check a hardware or home improvement store.
A potential ‘disadvantage’ from a risk management perspective could be that because your students are using an slippery surface you need to take extra care to make sure that each student is capable of maintaining their balance in a safe way. A matter of increased ‘possible’ risk.
The benefits would be in terms of using any such tool to improve fitness, add variety and provide variety. I use the glide discs with my individual clients.
I hope that this helps.