I started again in Master mode, the plateau was quite fun when it was a major struggle but after that it's basically the same. Nothing is really much harder and only combat is affected so massive parts of the game are unchanged.
It's also more of a frustrating change than a difficult one, since enemies are so much tougher and regenerate you can't really use stuff like environmental hazards, rocks, cliffs, explosive barrels etc to kill them in fun and clever ways, you just have to keep hitting them with a sword for longer.
I had a nice enough time redoing stuff though, the 2nd time was fine, the 3rd time is when it became boring and I stopped playing.