I have to say despite my disliking Hooper's decision to use THAT take of Hugh's Bring Him Home and the choice of Russell as Javert, I really am quite impressed by him making Cosette less 2D (thus more 3D instead) and inconsequencial by giving her a heart (with the addition of her pining for her 'dad' Jean when he left her), and making Marius a little less wet (choice of getting Eddie Redmayne to play that role helps tremoundously, because he makes Marius more intelligent and less self-indulgent than the stage version, also with more backbone, which I shall explain below).
I forgot to mention the addition of the 'flirting' between Eponine and Marius was a good decision too. Of course that part was also present in the stage version, but on stage Eponine sang about liking Marius' hair, which I thought was actually rather creepy. In the film version, she gently teases him for pretending to be poor when she knew his grandpa's rich. Most crucially she sang, in the film version, instead of 'I like your hair' or some nonsense like this, to "I like the way you talked", implying she's paying attention to what Marius' politcal views were.
By changing slightly the words they sang, Marius' response to Eponine's teasing about him pretending to be rich was that he didn't get a single franc without earning it, and that he alluding to 'burning his bridges' in terms of his privilege background, showing he's not just someone who's so shallow that he's almost ready to abundant his fight for the 'cause' just because he wanted to bonk a lady in a bonnet.
Then again, I didn't like how Hooper seemed to make Enjorlas appear quite harsh towards Marius. I always have this impression that Marius and Enjorlas are really close mates, and when on the stage version, as Enjorlas sang "Red and Black", he didn't come across as reproaching Marius, but more like encouraging and exhorting the latter why they were involved in the 'freedom fight' in the first place. I don't know, the three stage versions I watched at different times ALL came across as Enjorlas being less high-horsey, a little less in-your-face intensity that Aaron Tveit was directed to play him in the film. Maybe it's just me... Aaron had a fantastic voice and he sang Enjorlas' part beautifully though...