The banquet is a very prominent story that delves back in the past and sets up a lot of the future storyline. Adding Jaskier to it felt like a good move, although I felt they could have utilized him a bit better. The other changes weren't major and worked well enough. Again, I feel the short stories are (or at least feel) a bit rushed, but I think that was always gonna happen being translated to television. Something the writers are struggling with, is really integrating the humour into this dark and gritty world. At the moment, it feels like they are two separate things and that makes that the mood and setting sometimes change so drastically, it almost doesn't feel natural.
Something that annoys me a little, is the lack of external world-building. Characters just throw names of nations and cities out there, such as Temeria, Cintra, Lyria, Aedern and Nilfgaard. That's all well and good if you've read the books and therefore understand where they are and what their connections may be. I can imagine that for new viewers however, it feels like a lot of information that isn't really connected into a living world. I hate the comparison, but on this front, the show can and should learn from the first few seasons of Game of Thrones - were they did a really good job of not just throwing names out there, but making sure you understood what it meant.
All in all at this halfway-point, I am certainly enjoying the show. As it's the first season, there are always gonna be points of improvement. There is definite potential here, I just feel like the writers need to grant certain aspects a little bit more breathing room to develop and really dive into the potential of this world and it's characters. At times it feels too much like a fast-paced, generic fantasy show, which the Witcher really isn't.