Almost done with the game - the only bosses left are Father Owl, Demon of Hatred and Isshin. And, to be honest, I think I will leave it as it is.
When I was younger (<25) I really enjoyed trying something for 20+ times to finally beat it. Now I feel I't just not really a time good spent. What is really annoying about Owl and Isshin fights - they designed them more like a puzzle than actual boss battle. You need to exactly follow proper steps / reactions in proper moments, if you don't do it, you are done. Not much area to improvise or be creative, more like tedious memorize / implement. While fighting Friede, Gael or Orphan solo, I never felt this way.
I don't regret playing the game, would rate it probably around 7.5/10. Nowhere near Dark Souls though, and probably will never play it again (not much reason to do so with zero weapon variety).
I'm curious, can we add a poll to this thread about how many tries it took Codexers for Isshin? Options: 1, 2-5, 5-10, 5-15, 15-30, 30-50, 50+, never beat him.