I read half of the regulators before putting it back, it's not that I didn't like it as such, I read it straight after Desperation - and that was a long book that didn't really hit the heights I was expecting of it. I think I just had a bit of overload with Tak and the rest of the characters. I think a fresh read of it from the start about 6 months or a year down the line would probably go down better.
Misery - I got through about 60 or 70 pages, didn't like Paul as a character, and Annie is the "baddie" so I had no one to root for (I honestly didn't care what Annie was doing to him), throw in the fact that it's basically a secluded limited character novel - which was my main problem with the shining - and I was never really going to like Misery.
I started Cell, read about 40 pages and thought "another time maybe" - it did enough for me to know I want to, and will read it all, but for some reason, that just wasn't the time. I read those few pages quite disjointed, 7 or 8 pages one night, 10 the next, none the night after and so on, and I felt that the initial "pulse" should be read quite swiftly in a few sessions.
Finally, Dark Tower: Wizard & Glass - I know I'm repeating myself a bit here, but I was disapointed with DT Wastelands, didn't like cliffhanger end, didn't like how W&G started as the end of Wastelands, then when it did get going again, and they all got back on the path of the beam, I was just getting into it, then it stopped dead for a huge back story. I know now how good that "Susan" back story was, but at the time it was not what I wanted. I stopped here and reread one of the biggies (11/22/63 or IT, can't quite remember) then carried on.
Sorry about the length, I'm turning into
Walter Oobleck