I was fine with the ending. It made complete sense in the context of the series and how it all started. That being said, the last 3 novels, overall, really were not up to par with the 1st 4 books in the series.
None of the other books were on par with the first book, which was impressive in scope, especially given that it is the shortest of all the books, and more of a novella from his short stories. It remains one of my favorite novels, to the point that the over-sized paperback edition I have is about to fall apart from all the re-reading I've subjected it to.
That said, I found the entire series to be a worthwhile waste of my time. I enjoyed the characters, the setting, the conflicts and the resolutions. I have not read anything else by King, but I never felt lost when he interjected other peices of his work, or alluded to them.
There are times that I regret completing the last book, even after his warning. I put the book down after I read that and thought about whether or not I should take him to heart. But as he said, I'd come a long way with him, over years and years of waiting and then devouring each new installment. I didn't need to know, but I certainly
wanted to know, and I felt like I'd earned that right.