This Might Be a Good Unity Addition
3d Coat is already using it.
This thread has a more useful title. 
They didn’t use search either, though. :x
Typically don’t do forum searches each time I post. I did notice Dreamora thought it used 4 times the vertex count. That is incorrect. It lays out all polygons in one UV set but disperses size based on usage. IE you can tell it to make the polys in the face larger then the rest etc…
Zbrush uses a variation of this and is fast even with millions of polygons.
That’s really bad etiquette. And I didn’t use the forum search, just Google. “ptex +unity3d”.
Actually that is more or less correct since each polygon face is a separate UV shell which can potentially quadruple the vertex count.
Well that may be true in a worst case scenario. But that’s forgetting that UV mapping takes it’s own overhead. And that the savings in texture map size is huge. As I said earlier several of Zbrush’s tools have used this method for a while.
For me the biggest drawback is the resulting texture maps look like a tightly packed grid of squares. and are very difficult to clean up in a package such as Photoshop.
this works well