Most of the gripes about this film are about the implausibility of the time travel, holes in the plot, contradictions, and the "impossible" ending.
I really didn't mind most of that. I put it aside for the sake of the story. Although I must admit, the ending will leave you scratching your head.
Denzel Washington is his usual solid self. The guy can make any bad movie better.
My biggest gripe is the director's approach to filming. Scenes flash by so fast and there is so much blurred and jerky camera work, it's just unnerving. I guess the idea is to keep you hyped up, but it gets old. Director Tony Scott is best known for largely mindless action films with lots of explosions, car crashes, etc. I think a better director could have made this film more thought-provoking with less emphasis on showy camera work.
Deva Vu is not totally bad; neither is it great, but it is entertaining. But that ending.....! If Denzel is killed in the past, how can he be alive in the future? I've read explanations, none of which really made sense. The ending apparently borrows from Jorge Luis Borges' short story "Garden of the Forking Paths,' or at least that's my guess. It's worth reading, and it's a lot better than this movie.
Worth a watch if you're in a particular mood for something frantic.