To summarise, I enjoyed this film for what it was, a pleasant way to pass a few hours when you don't have anything better to do. If you want a high quality, serious adaption of Dickens, then don't see this one, see the ITV adaption made a few years ago with James D'Arcy and Charles Dance. The main critisms have to be the cast. Romola Garai as Kate Nickleby was simply terrible. Dressed 18th century, acting 2003. Totally mis-cast and put to shame by the superb Anne Hathaway. I had been told that Charlie Hunnam as Nicholas was by far the worst actor there. I disagree. Yes, his performance wasn't great, but you could see that he was trying hard. Just not quite good enough as an actor. Garai was worse by far.
Despite this, there were a few stars, notably the Squeers family (with the exception of the son). Evil, yet hysterical. Also Jamie Bell as Smike was fabulous, as was Nathan Lane as Mr Crumbles. I just loved Jim Broadbent as Mr Squeers, great to see Jim stepping out of the 'nice guy' role, yet still retained the affections of the audience.
See this film if only for Jim and Jamie, just be prepared to overlook the duds.
The DVD extras are almost worth the cost on their own. The 'cast on the cast' section is well worth a look.