Yeah, the constant griminess is just as annoying in its way as the overly-scrubbed look of the '57 film. I know they wanted to emphasize the misérables aspect but it's constantly filthy, constantly rainy, there's barely any difference in grime and murkiness between social stations, and the general effect is no hope or contrast whatsoever--even Marius and Cosette are unduly grim and never seem to smile! The students are vaguely tattered and covered in mud, Valjean's apartment is a dim unplastered hole in the wall, his death scene is melodramatic instead of peaceful... there's a sort of levelling effect when everything is horrible all the time.
One of the most astute comments made about the design for the new tour of the musical is Hugo's love of chiaroscuro. You can see it in his artwork, but it's also clear in his writings, where he often plays on contrast and paradox with no other purpose than artistic effect. We joke about his verbal tics and his fondness for abysses and shadows and sepulchres, but he's just as fond of horizons and stars and lightning. It's the old grotesque/sublime interplay in action. I don't offhand recall seeing a film that made good use of that in the design.
[Dieu] entend ta voix, ô fille des hommes! aussi bien que celle des constellations; car rien n'est petit pour celui devant lequel rien n'est grand.
- George Sand, Les sept cordes de la lyre