My likes:

• It was exciting to get a new "part" each week, especially when the warning at the beginning said "contains strong language, flashing images, and scenes you may find disturbing"
• A lot of the music was really good. So were the sound effects.
• The scene with the glowing Laura orb was beautiful. 
• The scenery was magnificent. 
• Some "Parts" were awesome. If I remember correctly, I particularly enjoyed 4, 6, 7, 9, 10, 11, 15, 16, and 17. So that's half of them. 
• I actually enjoyed the Dougie Cooper scenes and found them funny. I wasn't as desperate as most people were for Cooper to wake up. I have the box set of seasons 1 and 2, so I can watch the "normal" Agent Cooper whenever I want. 
• I liked Janey-E, especially in that scene where she gives that money to those criminals. 
• The scenes with Ben Horne were a joy to watch. 
• Jerry's scenes were funny. 
• Everything with Mr C was exciting. I was always wondering what he was going to do next. 

My dislikes:

• Many scenes were too slow.
• Some of the acting was really bad, with really fake sounding dialogue. It's like David just gave them their isolated lines, filmed it, and said, "Yeah, that'll be fine," even when it wasn't fine. 
• Much of the CGI looked rather amateurish. Well, it's relative. If that was a college project, perhaps it would get high marks. But for a professional release, they could have done better. 
• Many story arcs didn't go anywhere.
• Part 18 was an insult to the previous 17 Parts. The other Parts have every right to be offended. Even if Part 18 is a work of art in its own right, it's like spraying some graffiti over some precious oil paintings. It may be beautiful on its own, but its existence destroys what went before it, and that's too high a price to pay.

To elaborate on things some more:

David Lynch has said that he believes the artistic process is more important than the end result. I think that's the problem here. David did this project in the way that was most satisfying to make, rather than creating an end result that was most satisfying to watch. 

This is why we have scenes that drag on too long and scenes with bad acting. It's because the most fun thing for David was to just give the actors their lines, shoot a maximum of 2 takes, then move on. No time to rehearse, and no time to keep doing retakes until they get it right. Why? Because that would all be a tedious process and would take the fun out of it. 

Tied in with all this is the whole secrecy thing, and giving actors only their lines. This means they didn't do read-throughs in groups to see whether the scenes flowed well. What seems good on the page might not actually be good when it's performed. 

Then there is the issue of it being 18 Parts all written by the same two people and all directed by the one person. That's a HUGE project, and something I definitely couldn't do. It's no surprise that a lot of it was rushed. Kyle himself has said that the final scene was filmed in just 2 takes, then they quickly moved on. So, no time to try lots of different variations to see what flows best. No time to fuss over it and craft it to perfection. A rush job.

That's the difference when you're making a normal length movie. Every moment counts, so you need to finely craft every scene so it fits perfectly within the flow of the movie. An 18-part series is a lot for just two people to write and one person to direct. In such a huge project, there is surely going to be an overwhelming feeling of just trying to get it all done. 

Disclaimer:

I'm no film expert. These are just my opinions.