The buffet was a great option - IF everyone in your party wanted to spend a CS credit on a meal. I'm sure it drew guests in from other resorts. But it was a horrible option if you were staying at CSR and 1 person in your group wanted a full breakfast while another person in your group just wanted to use a snack credit on a bagel and use their mug for a 'free' beverage - it was impossible to sit together to eat. People having the buffet had to sit in the main PM seating area; people just getting coffee or using snack credits had to stay outside the PM area.
So, it was a cool experiment, and was great for some people, but I'm sure it resulted in complaints from actual CSR guests. And, of course, it may have ended up costing Disney a bit more for the food, too; never a selling point for the company.