I used Philosopher's Stone before it was cool.
I used to be like, the only one(in my bracket) to get it before Heart of Gold and Wriggle's Lantern was nerfed, now so many people use it.
Philosopher's Stone was just as good as HoG and Wriggle's before they got nerfed, now Philo Stone beats them easily.
Philosopher's Stone is specially good because it can be built into Shurelya's Reverie, which is a great item on ANYONE.
It's HILARIOUS when your whole team has Reverie. You guys should really try it out.
Philosopher's stone gives you free hp and mp regen early game, which gives you great farming and laning presence. Late-game, turn it into a Shurelia's Reverie, or sell it to get your money back.
Imo, Philosopher's Stone is overpowered, and has been overpowered for a long time, and people are just realizing how good it is now.