Most of the reworks have made the champions more interesting so far. The sion rework has worked out pretty well for him. He was either completely useless or soooooooooooo far ahead he could oneshot your entire team with one shield. someone who was good with old sion was like playing against a zed akali and katarina in the same lane. You're not going to have any fun and you're going to die a lot.
Veigar's changes to q are great. stacking is faster and safer. His stun cage is incredibly harder to hit now without a doubt but when you hit it you're taking half the enemys life most of the time pre-6. easy to force a flash.
tristana...gods I want to like this rework but it's just not trist any more. her range is low as hell and so is her attack speed. It's just not right. Easily the worst rework so far.
The ashe rework is iunno yet. She feels better as a champion but I simply don't know yet. Give it a week or two and ask again. I feel like she is going to be strong despite not gaining any mobility. I will say her E cooldown is way to long as it is right now.
Never really played zilian before so I can't really speak on his rework but it seems decent enough.
Now for the upcoming karma changes, they seem like they are going to make her stronger in a new way. If I remember correctly her tether is going to give anyone who attacks the target more damage and %healing. I talked to a karma player and he can see how it can be insane so I'm looking forward to it.
Now there is a rework coming that I do worry about quite a bit and thats the poppy rework. I know she needs some reworking and quite possibly on the level of sion but damn I hope they keep her e and q in some way.
And just so there is no confusion I can sympathies with you about reworks since I lost trist who was my main goto champion and she's dead and gone. but when you look at the reworks without an emotional connection most of the reworks made the champions better even if they don't have the numbers balanced out yet. No one wants their favorite champions drastically changed but no one wants their champion to be completely forgotten as everyone else gets stronger to the point of being completely useless.