Mtnbkr and I watched it last weekend.
Chris, based on something I found in a discussion here when the movie first came out, that WAS the Horn of Eld in Roland's pack, but it was never mentioned in the movie, either directly or by allusion.
As a movie based on the book series, yeah, it really freaking stank, as in very disappointing. Held up on its own, however, and removed from knowledge or comparison to the series, it was an enjoyable movie. I'm still very disappointed that the movie let down an actor of Idris Elba's monumental talents.
But in our post movie discussion Chris and I came up with a very appropriate, and very direct, comparison... The 1984 version of Dune. For people who have read the books, Dune was one of the most horrific movies ever made. It also came, in original theater release, with a glossary sheet that was handed out as you entered the theater (that's when I knew there were going to be REAL problems).
Yet, in retrospect, I've found that over time I've come to really enjoy Dune, IF I divorce it from the book, which was just incredible on so many levels.
So... Dark Tower is worth seeing, but you have to work hard to separate the movie from the books. If you can't, you're not going to like the movie at all.
Oh, and something I found out... there's going to be a TV series, supposedly coming out later this year, that will fill in a lot of the gaps in the movie.