I think that right now the arena functions amazingly well and as a person who lives about 12 minutes away the impact on the 'hood has been overwhelmingly positive. I am nervous that further developments will swing things the other way.
The parking situation and public transit use for basketball and concerts may not fare nearly as well with the Islanders. Hopefully, the LIRR will be a viable option for a lot of longtime fans.
The food in the arena is passable - certainly not bad enough to keep patrons from eating there (I am partial to "The Elbow Room" mac & cheese), but not nearly good enough to compete with some of the options outside. Who knows what the addition of more places like the promised Tony Roma's will do. And, when the scaffolding comes down and the new BBQ place in the old tile store opens, and the shake-shack opens, there may be a lot more people milling around longer before and after the game.
Also, the construction of more high-rise housing is a big mystery. Same goes for the government office building on Atlantic (I'm hoping it spawns a Lenny's).
There are potential positives as well. That bike area is totally safe (or so I hope) during events. It's just tucked away opposite of the main entrance so a lot of potential riders probably don't know it's there. Also, I am still waiting for my CItiBike key, and I can't be alone, so I would bet that there will be a lot more riders whenever that is worked out.
The problem with the surrounding retail is that some of it is clearly a great fit for the arena area. it's too bad, but "Cake Ambiance" can't expect a ton of foot traffic before or after a basketball game. Same for a few of the other niche businesses. Maybe the volume of foot traffic will work in their favor, but I don't know.
I do know that it seems like crowds have done a real service for places like Melt and Bark, and places on Vanderbilt and down Flatbush that serve food and drinks are benefiting without being totally overrun. For now.