No, people have the right to be upset. I already explained why the game should be 1080 and think it's a bit ridiculous it's not. I'm glad people are making noise about it. Hopefully, Ubi will learn.
At the end of the day, if you like Assassins Creed, which I don't no more (I did but find it sickening their annualizing the franchise) I wouldn't let 900p stop me from getting the game. For me the difference is minimal. A good game is a good game and not by its resolution. I'm not going to not buy Halo because the resolution is 900p. If the game is good, it's good. And from first hand, it's not a drastic difference but this is imo. You can always buy on PC.
But maybe not buying the game is the right route in this situation to show discontent at something that is possible. From the sounds of it, it seems like poor management/timetables is the reason for the resolution. They usually work at that stuff last in optimization. Unit is not graphically impressive.
So lets let Ubi know!