Good feedback from friends of mine who fly them often to Vegas from JFK; they won't fly anything else but. National's unique Frequent Flyer program was also an attraction to my friends, so you may want to go to the National web site and read up on it.
To the doubters, my friends tout National's good service and on-time flights (!) that has been their experience. Combine that history with their decent Frequent Flyer program, and you should be pleased.
[This message has been edited by vamsdw (edited 09-09-2000).]