I tried it on Ryze with a Muramana (among plenty of other mana items). I could topple towers, burst squishies, and keep tanky foes within my reach long enough to take them out.
The AoE Proc slow felt kind of like cheating when used on a ranged unit, especially with how much tankiness it offers.
IBG instead of FH on Ryze is rediculously powerful. Even without Manamune/Muramana.
I also imagine we'll start seeing Yorik build it as well.