Wolfick
I don't even know how to respond to the "Creator's Thought" this time. The manga is good too, I haven't noticed any changes before the mugen train arc, but I also haven't seen mugen train or anything passed that animated.
They didn't make changes afaik. In fact, it is truer to the manga than many others I have seen. The excellent art and animation breathe new life into it in my opinion though, especially as the way the author has designed many scenes, characters and plots resonates with the viewer. The manga, and I describe this with no ill intention, is what I would consider b grade artwork, and the anime covered this flaw. A great story can break through artwork level, as can be seen by the leading example, One, and his... scribble.