3 for atmosphere
4+ for service
5 for the food!!
As buffet service goes, Inti is great - the food is kept fresh and warm (or cool, where appropriate). Like many commenters here, I don't know "authentic" Peruvian - but I know what tastes great. Make sure to try as many sauces as you can. (Why aren't they for sale at the counter?)
My only caveat is that the buffet dinner is a touch pricey at almost $26 - but there's an easy way to justify the cost: come hungry, and eat well.
You'll be glad you did.