Out of the buffet chains I've tried at the higher end hotels, I liked the Bellagio one the least. My friends and I went for Sunday brunch, and there wasn't much of a line when we went. The price was about $30 something dollars plus tax.
The selection of food wasn't all that great or delicious. I felt the prime rib pieces were a bit small, and the crab legs were only "cracked" and not split in half, though my friend said they were split in half for dinner.
Most of the other food felt like standard fair buffet food, feeling very uninspired compared to other higher end buffets. Of the items I tried, they didn't taste all that good, causing me to end up eating more prime rib because nothing else was all that appetizing.
The dessert was also not all that great (they didn't have creme brulee either :(), and most of it tasted rather boring and kind of all the same, in the sense that it just tasted like sweet food without any character.
Definitely a pass for me in the future, since there are so many other buffets in the Vegas strip area.