My friends there all seem to think its all a good thing for Las Vegas and NV. They see it as another way to draw people from CA and AZ, and in addition to coming for a game, some will spend money in hotels/casinos/restaurants/etc.
In vegas talk, they call all the money coming into the casinos and restaurants from events as "the drop". The NHL's nightly drop into the vegas economy is over well over a couple of million.
Multiply that 5 times for nfl events such as the raiders and the super bowels.