It seems a rule that every martial arts actor must make a movie in which he plays multiple roles. Jackie Chan, Van Damme (twice!), and now Jet Li. And it also seems a rule that the results must be not very good - here, certainly, most of the best bits are in the trailer. The setting is not just our universe, but all of them, through which Bad Li is rampaging, mopping up his alternate selves, and sucking up their energy. Now there are only two: him and Good Li. You can guess the rest, right up to the final fight in one of those deserted factories only found in action movies.
The key problem is, why bother to employ Li (and twice!) if you're going to CGI the action sequences and, inevitably, use a stunt double to let him "fight" himself? It certainly ain't for his acting ability, and the infinite potential of parallel dimensions is largely reduced to Al Gore being president in one. Jason Statham struggles bravely as a trans-dimensional cop sent after Bad Li, while Carla Gugino runs around wide-eyed, so someone can explain things to her, until she is no longer needed and is efficiently disposed of. This passes for motivation in the Li-verse. The effects are certainly well-done, I liked the ending, and there's one jaw-dropping moment where a cop becomes the filling in a motorcycle sandwich, which reaches the FM!RT! level exemplified by The Bit With The Bus in Wong's last film, Final Destination. However, I will repeat again: if you've watched the trailer, you have already seen 90% of what this film has to offer.