Thanks man, I will get something brewing for the blog soon. Works kicked up a bit lately, so not as much free time.
I think the cornerstone of knowing when to add the x-step is when you are honestly feeling the leverage from a stand-still. It is so much easier to get and keep the feeling of real leverage from a standstill.
You can tell when the leverage is getting there, because the feeling is completely different.
I can put myself into all the right positions w/ an x-step and NOT feel the leverage.
The best way I can describe the feeling is the wrist tightens around the right pec and there's a feeling of the disc changing directions. The disc feels heavy for a moment, like you've weighted the disc... and then it ejects with a force that's greater than you think it should be.
If you can throw a teeBird 350' from a stand-still I would wager that you're ready for an x-step.
Unless you just happen to be the most graceful dude in the world, adding an x-step will most likely remove some degree of your feel for the magic. It's just a hard movement to merge with staying balanced / upright / braced while simultaneously guiding into the power pocket and then leveraging the pooh out of the outside edge.
That's why, I believe, you see many guys who can full hit with perfect form - take a very nominal x-step. They know where the real power is coming from.