I've been using the face and body and my hubby using hair treatment plus supplements. They work great for us. Our friends saw the progress and started using them too. To be honest though, people do react differently to any products. I can say 90% see the diff while others may not. The worse your skin is, the more immediate difference you'll notice.
As for the reason that nuskin strictly insists on using its own products is because the spa settings work with + / - ions. The face gels contains that. It first pushes the - ions gel into the 7th layer of skin and then uses the + ion gel to attract the - ions back out along with toxics and water retention, etc.