The lacklustre Dune mini-series did a fair job of covering most of the novel, but was let down by some poor cast choices, mediocre design and sets and a limp script. I wanted to see the sequel more to see how the story of Dune continues, rather than looking forward to more from the same production team. I've read and enjoyed Dune, but never the sequels as I've heard a number of times that they aren't as good as the original. So I'll be unable to judge whether this is a good adaptation or not.
Frankly, the first episode is a mess. The story feels mangled and despite being over an hour long, very little seems to happen until right at the end.
The second and third parts move the story forwards about twenty years and feel far fresher, with new characters introduced and a return to a more epic feel and it all feels more exciting. However, the story still feels quite disjointed and the other big problem is all the talk of "The Golden Path" which is barely explained, despite most of the story revolving around it's importance (I checked Wikipedia to find out what it all meant after).
The production is still let down by the tv budget occasionally - the tigers look like they came from 'Ice Age' and Leto's transformation into the worm and his superpowers are a bit poorly realized. When Leto starts screaming like a Sandworm it's unintentionally hilarious. I'm not sure if it is more explicit in the book, but the series seems to hint at something incestuous between Paul's children which is bit creepy.
I hope Susan Sarandon didn't get paid much for this, she simply hams it up to very little effect. Despite switching in Alice Krige as Paul's mother seeming an odd thing to do, at least she takes it all seriously and blows Sarandon off the screen with her quiet presence.
I have to admit it definitely improves towards the end, but I think we're still yet to see a definitive Dune adaptation.