I really like the choice the rune system gives.
I really feel like I have options and I am trading things off when I choose runes.
For example, I always change up my runes on Lulu depending on the matchup. I will take scorch and absolute focus into matchups where I want to bully people, while I'll take celerity and gathering storm into matchups where I feel like we'll need to wait it out to late game.