Sushi Mon is a real gem! It's far enough from the Strip that I doubt most tourists will ever hear about it, but I'm really glad I asked Yelp (and my local friend) where to eat sushi on a Friday night.
Sushi Mon does ACYE sushi (all-you-can-eat) the only way you can -- by ordering off a very extensive menu, and ordering more rolls whenever something catches your eye or when you realize you're still hungry. (No stale rolls under buffet glass here!) This only works if the restaurant has great service, and luckily, the wait staff is very prompt here.
If they still have it on the specials menu, you have to try the pastel roll. Unhealthy, for sure, but oh so yummy.
The only drawback was waiting for 45+ minutes for our table on a Friday night. In their defense, we were a pretty big group. We ended up killing time by stocking up on snacks and toiletries at the Smith's across the parking lot.