I just did the Buffet of Buffets earlier this week. It's $47.99 plus tax now (for TR members) and (as mentioned) a $15 surcharge on Bacchanal and the Rio seafood buffet.
To get the most value, you definitely want to start with a late dinner, then do breakfast, lunch and an early dinner the next day.
I planned on hitting 6 of the 8 (doing TWO dinner buffets both nights), but ended up only making it to 5. I was too stuffed.
Flavors (Harrahs) was my least favorite. Blah.
Paradise Garden (Flamingo) wasn't much better.
Spice Market (Planet Hollywood) was good.
Bacchanal (Caesar's) was phenomenal, WELL WORTH the extra $15. So much great food.
Le Village Buffet (Paris) is awesome for breakfast.
Next time, I hope to hit Carnival World Buffet one night. I have no intention of doing Emperor's Buffet (The Quad) or the Seafood buffet (Rio).