I recently watched two King tv movies/miniseries I hadn't seen before: The Stand and The Tommyknockers. I read the stand a couple of times in the 1980s and read the unabridged version around four years ago, so the details of the book aren't cemented in my mind. But it still felt like a lot of characters were missing details and the miniseries wasn't as rich as the book. Not really surprising. What did surprise me is that I didn't hate the miniseries. I thought it was okay. Some of the portrayals didn't really work for me but some were pretty solid (Gary Sinise). A nitpick I have is King's appearance in the film. It really took me out of the moment and he kept popping up again.
The miniseries script was based on the original edition of the novel. Only one scene was taken from the unabridged version, so if that edition of the book is freshest in your mind, it's no surprise you'd feel things were missing.
I do tend to give the miniseries some slack when it comes to details. The original version of The Stand
was about 800 pages, and that's an awful lot to squeeze in, even considering the show had about 6 hours of airtime to play around with. It's much the same problem Peter Jackson and his collaborators had with LOTR: deciding what advances the plot and what, while interesting, is basically filler.
I had my issues with the cast as well. Some were flat out awful (yes, Molly Ringwald, I'm talking about you), and others did credible work but just didn't fit the role (much as I like Jamey Sheridan as an actor, he didn't fit the character as King wrote him).