For those people who are saying that why did they changed the story.. Bro.. This movie shows exactly how the story is in the novels(except mito part) .. Kirito and asuna first meeting was supposed to be in a Dungeon.. Not in the boss meeting...the anime showed it wrong...
Now for the second part - kirito asuna continued their journey till the 25th floor... Some may find it weird because when shown in the anime.. Asuna didn't knew kirito well when she was vice leader of KoB.. But even the author knows about it.. And he clearly said that it will somehow contradict the main sao story.. ( so if you have problem with sao-p series.. You can stop watching it.. and wait for 4th season of SAO
3rd - i dont think so mito is a horrible character.. Like other people says. She is introduced smoothly into the movie..without changing the main theme... I think people just cant digest the fact that she wasn't shown in the main anime.