I think, I find it much more easier to write this review from 2 different points of view: As a standalone movie, and as part of the Sword Art Online franchise.
Well, as a standalone movie it was a pretty good one. Comparing to other contemporary movies, any movie that keeps me invested in the story and don't want to fast forward is a good movie for me. It is nice to see the same familiar story from a different perspective and how the same events are intercepted differently by each participant. Although the movie is pretty short, we could still experience a character development (although I'm not sure we want too) and story development.
As part of the SAO project... After reading the synopsis, I didn't have much expectations. How many of you would want to see a movie that they have already see? With the same characters? But they did it! Somehow the SAO team crafted an interesting experience, based on a well known story. Having said that there were too many things that didn't heads up if you try to connect the events from the movies to the events from the series (And I'm not talking just of the actions that took place in the movie, but the character's reactions that just don't heads up, sometime it felt there were 2 different set of characters).
I must say, without any doubt, the producers of this movie decided to take the road less traveled. I think I can count on one hand the number of movies that try to achieve this: creating a "prologue" that interacts with an existing plotlines in so many places. I really appreciate the fact they try to use this technique to deliver a unique and interesting experience to the screen, However I think this movie could have been better entwined with the original story.
Moreover, I'm not sure why they have picked this period of time and that question for a movie. There are far more interesting (and easy) question to base a movie on. For example What happen in those 2 years gap in the series? How the Knights of the Blood Oath came to be? How Asuna joined there? Where and why Kayaba did? And some more question that I find much more answer worthy than the question they try to answer in this movie.
To sum things up. I think this is a real good movie and can be watched even if you have no knowledge of SAO at all. If you saw the first season, you won't be disappointed just a little bit confused (I know I am) and hoping that the next movie would shed more light on far more interesting questions.
