Today I went and took my new catnip item out for a spin on the hard boss in the desert, Angra Mainyu. Rikku wasted some time berserk attacking the arm that was immune to physical damage but when she went after the actual boss she did silly damage to him. Yuna was able to use the dark knight ability darkness to keep the arms mostly dead which cleared the path for Rikku to obliterate the boss. Paine made herself invincible and stood ready to throw a phoenix down at Rikku if she died. I wouldn't say the fight was trivial but it was definitely easy. Catnip may have been nerfed but it's still pretty darn good.
With that boss down I figured it was a fine time to go finish the game. The end boss was actually a joke thanks to the catnip. It's a series of fights that presumably have hard components to them but since Rikku goes first and attacks for 19998 before the enemy can react... Splitting the fight up into lots of small fights where she gets to strike first over and over again bodes very poorly for the enemies.
I got a completion score of 55%, which is far short of 100%. It turns out I did a pretty terrible job of avoiding the plot which is what you need to do to get 100% in one playthrough. You have to do every side quest possible and often doing some of the plot will advance the state of the world such that you miss something. Assuming my wrist holds up I may try to burn through a second playthrough focusing on sidequests and see where that gets me. I'll still have that catnip so actual encounters won't take too long I wouldn't think.