tl;dr I like the Katarina update kinda, but some minute things and loss of options are annoying.
The little nuances that got changed about her annoy me the most, but some the bigger changes do irk me as well.
Starting with a minor non-gameplay problem I have is that I HATE her new sound design, it's just not as satisfying as it used to be. I can deal with the dagger pickup sound and some of her AA sound changes even though I hate them, but PLEASE revert her old R SFX on base skins, it was the most satisfying thing in the world, the new sound is just pathetic.
With minor things I hate, I'd like it if her Q dagger didn't bounce so far onto the ground. It makes lane trading annoying and clearing a gromp (small tangent on other jungle camps, smaller ones are somewhat hard to click on) a total pain since it always jumps the wall. Next would be, why is her E now a dash instead of a blink (I loved that old animation, super cool to zhonyas the middle of it) and why does it no longer put her behind targets? Just feels bad to me. I'd also like it if she could ward hop again, I know it was a conscious decision to take it away, but it really kills a lot her old cool stunts and ways to secure kills.
She just feels incredibly 1-note and braindead as a champion now. Her damage is just beyond garbage (.3% and .25% AP scaling on her bread and butter spells???) except on her dagger pickups which means you HAVE to utilize them. She's basically moved onto only having 1 core combo being Q>E>W>E>R now and she just feels slow since setting up daggers is slow so surprise flash shunpo kills are just dead. Personally, I'm just annoyed with a lot of minor things based on champion feel and her general flow now, but I still like her even though it's a bit less. I actually find that with the jungle changes and her new stats and kit that she can jungle preeeetty well with a 9/0/21 page. And since her AD ratios are actually pretty decent, I like building her a bit tanky with a lil bit of AD items like Triforce (lets you play a bit more aggressive with no daggers placed and lets you place them more frequently with the high CDR) and maybe something else like Sunfire or Sterak's into tank. Very sticky and still does decent damage with Dagger pickup and E spam + Triforce procs.