The PBE changes are overall a huge buff.
She loses her true stealth and her ult cooldown is back to what it used to be.
However, her Q does more damage, her E got a massive boost in damage, her shroud has a shorter cooldown early, her energy economy is much more consistent, and she's overall just tankier.
At level 3, Akali's Q's each cost 100 energy, and her E costs 30 energy. Since her bar is 200 energy, she can only throw out two Q's before she runs dry. Her passive autos give her 10 energy at that level, and she regains 10 energy per second passively. Right now, she also gets 40 energy when she activates her shroud. In 9.14, that will be doubling to 80 energy.
So, before, Akali's combo was Q(100)-aa(110)-Q(15)-aa(25)-W(70). At that point, she'd need to wait ~3 seconds to get enough energy for a third Q, or she could use her E. Alternatively, if she opens with E, she'd need to either wait an additional 3 seconds to get the energy back before engaging with the E2 (giving them time to walk to a better position), or wait an extra 2 seconds between the first Q and the second. In short, she can't use her whole kit without waiting for energy at that level. She needs more points in Q to spam it.
With these changes, she can do E1(170)-E2-aa(185)-Q(85)-aa(100)-Q(0)-aa(15)-W(95)-Q(0)-aa(10).
TL;DR: She will be able to use every single ability in sequence at level 3 for an absolutely devastating all-in, with three Q's instead of the old two and no downtime between abilities and autos. Not only that, but her damage is also getting a buff. A skilled Akali will be able to delete people.
The added kill pressure from more damage and energy efficiency is extremely worth losing the true stealth.