Time paradoxes make inherently confusing stories, so it’s critical that you connect with the characters and feel the plot has some value otherwise you’ll be left drifting. Deja Vu manages enough to keep you interested, keep you wanting to see more, and keeps you caring about the two main characters.
The screenplay is clever but doesn’t try to overstretch and there are no attempts to explain the paradoxes, and plenty of in-story explanations of why time travel is a really bad thing[tm].
The performances are solid, Denzel is interesting and believable, Paula plays the small amount of time she has on screen pretty well. I’m not entirely convinced their actions in the latter half of the movie make much sense, but I’m willing to suspend disbelief to let the story play out. There’s some action, some cute effects, some nice ideas and a certain level of suspense especially towards the finale.
The ending was kept hidden pretty well, and although I finally realised how it would play out just before it actually did it was worth the wait. No shocking last moment twists, no huge discovery, just a decent ending for a decent movie.