I wouldn't say it was a great movie but decent enough. Obviously it is quite scrunched up taking it down from 6 hours to under 2.
I saw the film first and now am watching the series and the series is alot more indepth (as you would have thought). It has more subplots/background on the characters. There are a few subtle plot changes but standout from the film. It also has some big names from the UK acting pool which may make it more interesting for UK viewers.
e.g.
Bill Nighy, John Simm, Phillip Glenister, David Morrisey, James McAvoy, Kelly MacDonald, Marc Warren etc.