I think what this arena does is make Brooklyn a destination for tourist and people from other parts of NYC-metropolitan area. Once you get past Coney Island theme parks, the Brooklyn Heights Promenade, and the Prospect Park Museums what is there to do in Brooklyn? Brooklyn needs to have a lot more involvement in a tourist itinerary and I think that an arena is a good way to give the borough more prominence.
Just imagine during nationally televised a Brooklyn Nets game they show the arena with a backdrop of those funky Ghery designed buildings. It may just work on people curiosities and make them check the area out. Of course with this you have to make sure that the area will be somewhat trendy via opening more restaurants, bars, etc. Also, connect the arena's accessibility to the New Brooklyn Bridge Park (via trolley, or whatever), which I'm sure it's going to be a great tourist draw as well.