Been there for basketball and hockey games. It's definitely not set up for hockey, the scoreboard does not line up with the center line. Also seen concerts at the venue which did produce great sound. The center would be better if there was more space, but being in Brooklyn I understand it is limited. Getting to this venue via public transportation is very convenient.
Lapin and I came here for our first hockey game. There was a line to get in but it went pretty quickly. Like most stadiums, we had to pass a metal detector and our bags were checked. We had nosebleed seats and apparently the opposite end of where we came in. The center is populated with restaurants and fun things (I got my face painted for free that night) along with free giveaways. I can't speak for the other seats but our seats had barely any leg room and we had to get up every single time someone wanted to get out. We had a hard time seeing the game, but there was a jumbo screen up top. The food prices were a bit on the high side, so I would suggest eating before your visit.
Let me start by saying, I am not an Islanders fan, but I do feel bad for the fans who have to trek to this arena. It is an eyesore outside, and it is no better inside. I have seen three games here, and the rep told us that this arena was not built for hockey. If you sit on the defend twice side in the upper level, you will have a huge obstruction which are your own seats, once the players cross the blue line you have to switch your vision from the ice and quickly move to the screen. There is no good parking locations nearby but subway is close. If you are thinking about going to see the Islanders, I would highly recommend saving your money to go to MSG or the Rock instead.