I practically grew up in New Jersey diners, so to see a diner laced with Las Vegas DNA was quite a sight. The Peppermill is precisely what it ought to be as a classic diner - giant menu, stainless steel exterior, breakfast all day. But it also has a full bar, a photographer and a clientele that is clearly a mix of locals, people starting their day, and people ending their day.
I tried the gyro (excellent), the onion rings (excellent) and an omelette (also excellent). They play the favorites and do them well. I strongly recommend a visit. You will have more fun there than any buffet on the Strip.