Did the movie "Let the Right One In" need to be remade, hell no!
Was the remake that was just recently released, " Let Me In", worth a watch? Yes!
The difference's weren't necessary, as the original was well crafted. They were merely the vision of the new Director Matt Reeves. He choose to flesh out some scenes that the original didn't, therefore it was more of re imagining than a shot for shot remake. I appreciated the gore of the new movie. Though I don't know that it added anything more by having it, it was just a personal preference of mine.
The boy Owen, in "Let Me In" seemed weaker and more vulnerable, than Oskar, in "Let the Right One In". Oskar was more of a morbid child (as he was in the book) and every thing that happened to him with the bullying and finding out about Eli being a vampire, was easier for him to accept, than for Owen.
Owen was more damaged and fearful of his surroundings. Justifiably, as his bullies were much more brutal and violent, than that of Oskar's. Even Oskar's parents were more present in his life, than Owen's. Who truly had no one, until he found Abby.
All and all, I like them for different things and realizing them as two different versions of the same story, both done well and we are all the better for it.