I saw it yesterday, and I thought it was a wonderful throwback to the magic of the 80s sci-fi film. It definitely has it flaws, some of them being the lack of deeper plot development.
However, there were some parts of the movie that just felt so real, as if it was coming from that time period. I thought all the kids did a great job acting, no over-the-top, extremely eloquent speeches, but they just talked like kids.
The final scene, which disappointed some, really clenched the film for me as a great one. Giacchino's musical score, which was for the most part fairly bland for most of the movie, really rose to the occasion. It truly captured the wonder of the finale.
I highly recommend it, flaws and all.