I really liked it....
I played AC 1, 2, Brotherhood, 3, and 4 so I'm fairly familiar with the concept and subject matter. The movie wasn't perfect, but I actually really enjoyed it. They probably should've spent more time in the past than they did, but I think they were really building the story in present time so that they could make sequels.
The route they took could take the remaining assassins on the run in a similar fashion as they did with Desmond in the games. Just my two cents.
The critics were overly harsh in my opinion.