Hi, Lola and Welcome to the DIS!
If you are talking about HotelDiscounts.com I HAVE used them.
I booked the Hard Rock with them when I was not able to get a reservation through the hotel itself (booked). I got a great rate, about $10 more than the Entertainment rate, they took care of everything and I truly enjoyed my stay.
My only warning to you is that your name does not show up at the hotel till 24 to 48 hours before you arrive. This really unnerved me because when I called the hotel the week before my trip they had no idea who I was! I called HotelDiscounts.com and they told me then. I think they should let people know this earlier, for obvious reasons.
I'm sure others have had varying experiences but mine was fine.
Hope that helps!