Read the book back in 2011-2012 when it first came out. I watched the show all the way through a week or so ago and I have to say that, if you read the book, it is pretty faithful and is a damn good show. That being said, I was amazed that, even despite it's roughly 8 hour running time total, they still had to leave out a bunch of sub plots and other plot points that weren't totally necessary to move the story along. I thought that at 8 hours (which is much longer than the running time of any previous King adaption save for 'Under the Dome' and 'The Dead Zone' which neither followed the storylines of the books much), they'd be able to fit everything in, but they still weren't able to.
All in all it was a great mini-series and is something I hope they do in the future with some other King novels ('Salem's Lot', 'The Stand', and 'It' all need remakes and could stand to have the Hulu treatment too).