The world-building is great, the OASIS is quite fun to imagine, as is all the related tech. The world outside, and the complications that arise from the game, are not very fun to imagine at all. It's unusually cheerful dystopia.
The pop culture references invading every page are never very well-integrated into the story. As others mentioned, it's mostly there to pander to nostalgia. They are fun at times, but a good 50% could have been cut, let's be honest.
The characters were pretty bland, but by the end I was admittedly invested in their fates. The twist related to Aech surprised me, and I really wish the book would have delved into that a bit more. It would have made a much more three-dimensional character, and there would have been opportunities for some poignant scenes.
Despite all of this, I gave the book 4 stars. Mostly for its entertainment value, and pure imagination. With a slightly leaner plot and deeper characters, this could have been both fun and genuinely great. Alas, it's just fun.