Some other viewers might have succeded to do an overall commentary, but it is in my opinion impossible. It is hard not to spoil but I'll do my best to explain what I felt without spoiling.
There are two main parts in the anime, that you can't unsee.
The first one was awesome. The plot was kind of simple, but efficient and enjoyable. The anime and what happend was consistent, and all the MMORPG elements were here, so a fan couldn't feel lost, what is great. At this moment, I felt stressed, scared, and the suspense was important. SAO was at this moment kind of a dark fantasy anime, and not a bad one.
The sad fact is that there is a second part. As I'm not going to spoil anything, it might seem imprecise, but I can summarize. This second part is ways too different from the first one. First by the atmosphere, in my opinion too "childish". Then, the total lack of consistence, of logic. I didn't feel stressed, I wasn't afraid for the characters, and the universe wasn't attractive at ALL. It was globally predictible and uninteresting.
As an overall commentary (finally), I'd say SAO started well, but it didn't become what it could have become. In my opinion, it should have stopped at the end of the first part. Second part is a huge joke that ruined the entire anime.
I'd still recommend you to watch it, as this first part worthes the time ; this was for me a great experience. But prepare to be deceived by the end.
