I was quite surprised to come on here and see bad reviews... but I guess if you watch this program expecting it to be a thoughtful satire of Dickens then you might be a little disappointed. This program is, in a word, silly- and it is fantastic at being silly! Someone mentioned that it has the 'usual suspects' of the Beeb getting together- something they saw as a bad thing. Now, I am a fan of Mitchell, Webb, Fry etc, but putting that aside- this program seemed to me like a group of people getting together and having a laugh. So yes, the actors seem to be typecast... but they're playing the roles they love to play.
I don't think they were trying to be clever or make a new classic, they're just having fun. There are lots of shout-outs to Dickens (and our modern conceptions/interpretations of Dickens- Mitchell's character literally swelling with joy being a good example).
No, there's not much substance. There's a hearty nod to the Dickensian plot, a liberal smattering of caricatures and a mob of cannibalistic urchins. There are false moustaches and clockwork hats. There are silly ideas, and clever ideas (the three clocks).
Don't watch this expecting a serious film. Get some popcorn, relax and enjoy an hour of pastiche. You'll get to see Webb in a leading role, and you can play 'spot the comedian' with the supporting cast. Stephen Fry makes a fun villain with a stunning selection of hats. Robert Webb gets cooked with onions and arrested for not being manly. Parkinson gets addicted to treacle. Watch it, you'll enjoy it. ;)