Not sure what all the HYPE about White Castle is all about. You can get a way better burger for cheaper at Shack Shake, Steak N Shake, Fatburger, or even McDonalds, if you want a late night meal, Del Taco is better than White Castle. I think people rate it in the nostalgia feeling and the memories, because it's totally not worth it.
The line did move fast and it was clean, but based on taste, no way. You're in Vegas, were you can get a gourmet burger for $6.99 (at Flemings Steakhouse) or a decent burger at local bars for the same price.