I miss the pure versatility that the old rune system gave you, but other than the allure of gimmick pages like full health regen Soraka for infinite lane sustain I understand that the new rune system is better.
I miss when Kindred would shred baron and dragon
I miss the braindead playstyle of old Aatrox.
I miss sword of the occult.
I miss that one patch where the 20% stronger heals/shields passive on
was stackable and Soraka was dishing out 800 HP heals every second and Janna had 2k health shields.
Definitely prefer new Fiora though.