Long story short (since "Les Mis" is sort of already the Obi-length equivalent of a story):
Jackman's a decent Jean Valjean, hitting some good high notes and getting stronger as the play goes on, though his voice (and most of the singing) doesn't hold up perfectly in the first 10 minutes or so...the whole opening/Prologue is wobbly until the Priest (Colm Wilkinson, the original US Jean Valjean, in a nice touch) shows up, and after that...
Things are mostly saved after Hathaway shows up as she's a BRILLIANT Fantine, that's an Oscar-Worthy performance right there, and she sells what's basically the style of the whole rest of the film--singing the musical, but doing it less operatically and more in a sort of "acting-singing" style that limits some songs but allows for some great emotive moments acting-wise, and that's basically her "I Dreamed a Dream" in a nutshell, I have to give her credit, she sang it pretty well on its own, but with the added acting and just all the atmosphere around her...it's easily a highlight of the 2 hour, 38 minute show, and if she's not nominated for Best Supporting Actress, then I just don't know...
Russel Crowe is the weak link in the cast, which isn't to say he's bad, but he has a rang of about two to three notes, it sounds like, and wears (until the end) the same damn expression on his face the whole play, through all 17 or so years it covers, that same Crowe-esque scowl...none of the songs with Javert are too great, and that really hinders some of the most dramatic moments of the piece, but his death is done very well, and he DOES look like he's trying, so points there...
The rest of the ensemble is pretty good (if not "amazing," so again, if that's what you're hoping for, you likely won't find it here) with 3 exceptions:
Samantha Barks, continuing her role as the friend-zoned Eponine from the stage version, is great, "On My Own" remains as great (if melodramatic) as ever...
Eddie Redmayne as Marius was surprisingly brilliant, that's a role that's usually only OK for me, he did a great job, and "Empty Chairs at Empty Tables" might be the best-sung song of the entire show in terms of combining technical and emotional power...
And Sacha Baron Cohen (someone I'm normally not a fan of) and Helena Bonham Carter are hilarious as the Thernardiers, they steal every single scene they're in, and they're in it just enough to where that's refreshing and to where that's irritating.
Same with the kids in this version...I've never been a big fan of children actors, but the Gavroche they picked does a good job for his age, and is in it just enough to show he's talented for his age and stops just before you might feel annoyed by a little kid popping up at the Barricades of this (rather epicly-shot) June Revolution.
(Though--although it obviously happens in the book and play--seeing a kid get shot on screen after Newtown made for an awkward and uncomfortable theatre for a couple minutes...)
All in all it's a good version, not at ALL the best-sung version, but good, it gets stronger as it goes along, Act I getting by largely on Hathaway as Fantine and the Thernardiers, and then Act II is far stronger in every regard--the songs are better sung, the revolution is shot brilliantly, and everything's just done better and with more power behind it...
Crowe isn't great as Javert, but doesn't kill the film; there are so many close-ups in this film it's absurd, but if you're there you're probably there for the music and as long as THAT is competent (and after those first 10 minutes it usually is) you probably don't care, and it's not at all earth-shattering or musically a version I'd listen to over and over...
But it was fun to see done on the big screen and, for the most part, if not earth-shattering, done well.