This weekend I was struck by the urge to jump back into ZBrush (after far, far too long) and finally learn how to sculpt seamless textures from scratch.
Rendered in UDK
Success! Today I think I finally nailed the process. This isn't a gorgeous material in it's own right (especially compared to Uncharted's materials, which I was what I was aiming for), but it's proof the process works and produces technically clean results without the need to touch up maps after the fact. It should be noted that absolutely no hand-painting went into this one- the diffuse is made up of masks and a photo, and the sculpt was made using a procedural rock I got from a maxscript. The whole thing could probably be reproduced in 30 minutes.