A current theory is that it contains the Philosophers stone, its certainly more important than just a rock.

If it's the Philosopher's Stone, why would Dumbledore say it was James Potter's Rock, or that he found it in Godric's Hollow? Then again it might be a big rock from Godric's Hollow that contained the (small?) Philosopher's Stone embedded inside. But could Harry Transfigure it if he didn't correctly know its current Form, or whatever the term is? Is it even safe to routinely transfigure the Philosopher's Stone?

Which holds a terrible secret.

It also holds the hint that Dumbledore gave Lily that enabled her to come up with the dangerous potion that made her sister Petunia pretty, enabling her to marry Harry's father Professor Michael E-V. Many people think this is the fabled "single point of departure from canon". Could be important, but it's hard to see how.

A current theory is that it contains the Philosophers stone, its certainly more important than just a rock.

It's certainly not the Philosopher's Stone. The only reason the stone isn't at the Ministry (or Gringotts) is that Hogwarts provides the absolutely best protection:

"I do not own it, that thing which Voldemort desires. It belongs to another, and is held here by his consent! I asked if it could be kept in the Department of Mysteries. But he would not permit that—he said it must be within the wards of Hogwarts, in the place of the Founders' protection—" Dumbledore passed his hand across his forehead. "No," the old wizard said in a quieter voice. "I cannot pass this blame to him. He is right. There is too much power in that thing, too much that men desire. I agreed that the trap should be laid behind the wards of Hogwarts, in the place of my own power" (Ch 79).

I can't see Dumbledore going and giving it to Harry to wear on his finger.

A current theory is that it contains the Philosophers stone, its certainly more important than just a rock.

It might just be a rock. It'd violate the rules of storytelling, but Dumbledore reasoned incorrectly, and the laws of probability are LAWS. *ominous thunder* That consideration could take precedence in an author tract like this one, Chekhov's Gun be damned.

This book is proof that Dumbledore intervened to make Lily Evans distrust Snape, who was the friend she is referring to. Snape whose entire existence is based upon his love for Lily had it taken away from him by Dumbledore. Quite a terrible secret indeed, but until you know that you think that Dumbledore just snuck into the girl's dorms to mess with their mind.

Where are you getting this? What makes you think he intervened to make her distrust Snape, and why do you think that's the reason things didn't work out with Snape and Lily? I don't see this from the chapter.

Also, what's the deal with Fawkes and the evil parents and him running away?

It's not like Dumbledore shies away from flat-out lying when it suits him. Unless you think lying in writing and lying in person are meaningfully different?

(Edit: Whoops, this is wrong.) Chapter 30:

Then Harry's mind clicked on another implication, and he looked down at the steel ring on his left hand's pinky finger, and almost swore out loud when he saw that the tiny diamond was missing and there was a marshmallow lying on the ground near where he'd fallen.

He'd sustained that Transfiguration for seventeen days, and would now need to start over.

Could've been worse. He could've done this fourteen days later, after Professor McGonagall had approved him to Transfigure his father's rock. That was one very good lesson to learn the easy way.

It's been a lot more than a month since then, but that's the last we hear of it as far as I can tell.