This movie died when Paul Walker did.

Rating: 4/10 (8 April 2015)

The filmmakers did the best they could in gluing what pieces they had together, but the fact is, this is an incomplete movie that is unengaging until the final two minute Paul Walker tribute - which isn't "really" part of the movie's story proper. Of course, there was really no way around this. The series main protagonist is "present" in the movie, but is himself not really engaged in any of the movie's happenings. Whatever Walker's original story arc was, and whatever footage he shot for it was clearly mostly excised. Given that this was intended to be the 1st movie in a new F&F "trilogy" then this obviously had to be done, as there was no way there could ever be a continuance or payoff to the story arc without Walker. His arc is instead replaced by Diesel and Jordanna Brewster talking about how Walker wants to be a good dad and is 'over' being Fast & Furious as a setup for his eventual exit at the end... but he's not really involved in these conversations, as that wasn't the original plan.
Nevertheless, you can't simply remove the protagonist from the story and remain engaged. And make no mistake, though Vin Diesel has given himself top billing ever since becoming a producer on 4Fast-4-4ious, these films have always primarily been about "Brian O'Connor's" journey, with Toretto as the deuteragonist in the later movies. And when you remove Walker's character, all you're left with is "spectacle", and Vin Diesel trying to be Superman. Regarding spectacle, this movie has few equals. However, it's ultimately meaningless if your protagonist is disconnected from it and has no stake in it. Regarding Diesel, his character simply isn't interesting without Walker as a foil and can't carry a movie on his own. His only real character connection is to Letty. Han is dead, Roman & Tej had established relationships with each other and Brian O'Conner in 2Fast2Furious, but never really establish a rapport with Toretto. The glue of this "family" was Paul Walker's character, and now he's gone. Nobody wanted to see Diesel as an unstoppable action hero in XXX or Riddick, and it doesn't play here either.
Aside from the aforementioned issues which were directly related to Walker's death, this movie has a few more issues. The first of which, is that it totally glosses over the death of Han. His death and bringing justice to his killer is the WHOLE MOTIVATION for the larger story. I have a feeling this aspect may have been affected by Walker's death, as they didn't want to dwell too much on character who died in a fiery car wreck like Walker did in real life. However, it didn't do the story any favors to be almost dismissive of the incident providing the characters motivation. Furthermore, it didn't make any sense for Sean Boswell - who spent a whole movie being mentored by Han, and thus has the strongest connection to him - to only show up for a cameo and NOT to join the team in trying to avenge him. Wasted opportunity to truly incorporate Tokyo Drift in with the main series. Finally, Jason Statham is by far the biggest "name" to be cast as the villain in a F&F movie, and I feel like they kind of botched it. The movie goes off on a tangent with Djimon Hounsou and Statham sort of disappears and didn't get the chance to shine as the villain like all the lesser names in previous installments got to. Really, too bad. F&F needs to learn the "Batman" lesson that more villains isn't better. Furthermore, there's no point in bringing in badass Jason Statham if Toretto can just straight up beat him up. You've completely neutered his character, killed any dramatic tension and there's no point to even casting Jason Statham then.
So, in conclusion, the movie was irreparably harmed by Walker's death. But even if it hadn't, there still would've been several missteps in it. If the plan for the future installments is Diesel as Superman, just kill the franchise now. On the plus side though, the stunts and "spectacle" aspect of the movie was top notch.