Other reviewers have already mentioned this but I can't stress it enough. Buy your tickets in advance online! After we joined the ticket holders line it only took about 20 minutes to get in, but people without tickets were waiting up to 1.5 hours to buy their ticket, and then having to line up for a second time in the ticket-holders line. Sure, if you've got time to waste and don't mind waiting in line (anyone?).
Also, it's really new and so it's fantastically crowded right now. For the love of God, leave the strollers at home! It was a nightmare trying to navigate though the sea of strollers and kids, and there were so many people with their noses on the glass that you couldn't actually get to the tanks to have a good look unless you waited for a long time. They have a few exhibits where you can touch baby sharks or rays. The kids loved it but, after the novelty wore off, I was left thinking it felt a bit cruel.
The Planet Jellies and the Dangerous Lagoon were the highlights. Being on a moving walkway as you are transported through a tunnel of sharks, manta rays and other marine life and being able to see the bellies of the fish as they swam over you was pretty fun.
My recommendation would be to wait until the hype wears off so you can truly appreciate it!