I don't see what all the hate is about. Surely on some level everyone knew what was going to be in store for our beloved gunslinger? He wasn't going to find happiness was he? I think he knew too and that drove him on regardless. I personally believe he expected to die at the top. Lets face it, he has killed hundreds, maybe even thousands to get there and he just had to see it through til the end.
One thing I didn't understand though, Eddie dies in Roland's world, so is there not another Eddie in another world? Like how Jake dies but is bought back again? And I think the horn won't serve a purpose at all in the sense of literal use, it's just one less sacrifice he has to feel guilt about.