'This Is It' showcases Michael Jackson in all of his creative genius. It gives you a chance to see into Michael's mind and see how he worked. Many people will watch this and some will think that he wasn't at the top of his game, but as Michael said himself 'that's why we have rehearsal'.
I personally loved this. I saw it twice in the theater and liked it even more the second time around. Not only do you see the work aspect of Michael, you see the person. You see how he was with the people who were giving their time to him and you see him in a different light.
I think even if you weren't a MJ fan, you should buy this. Because chances are it will change your mind and blow you away.