Thanks!
As the one that got to do most of the sanding/shaping and arguing with tile people that told us it wasn't HOW IT'S DONE, I appreciate the compliments

.
To answer some of your specific questions:
As Susan said, the epoxy was tinted with graphite to make it a dark grey, and then sanded flush with the stone. As it's precisely the same height and sanded to the same texture as the stone, it's very hard to pickout in many cases, and yes, it is the same matte finish as the stone.
When there was still a big swing in the color between freshly oiled and needing to be oiled, it did indeed stand out more as the stone became lighter in color. As the stones have gotten darker with time though, the seams bend in better and better. The patina that the stone develops with use also tends to make the seams blend in more as the years go by. Gotta love a counter that gets *better* with abuse
Making an apron front sink... Phew. I imagine it's probably doable, but I really *really* wouldn't want to do it with tiles like we used without ROCK SOLID support in all directions. The whole key to the system working is that the plywood substrate is very stable, totally encapsulated in epoxy so it doesn't expand/contract at all and is extremely thick and well supported. This ensures that the surface the tiles are bonded with never moves or flexes. My biggest fear would be that someone would step in the sink and that could apply enough pressure to make whatever you're supporting the tiles with flex. That would likely crack the tile and possibly ruin the sink, though you might well be able to fill the crack with epoxy and sand it smooth again.
I know that nobody *should* step in a sink, but people do all sorts of things like that all the time, I generally find it's best to plan on it happening so you can avoid heartache when it does.
Basically, if this is what you want to do, I'd design/build a bullet proof box that has no flex to it at all (if it's wood, fully encapsulate all parts with epoxy) and then basically line it with the tiles. If there was anyway to swing it, I'd probably splurge on getting a soapstone sink that was fabricated from thick slabs though, it would probably help me sleep better at night.
If you do decide to tackle any part of this project, feel free to ask any questions that occur to you, we'll be glad to provide any help we can. It's a lot of work, and you really NEED to wear a good quality respirator, not just a nuisance dust mask, as the soapstone dust is terribly fine stuff and very bad for your lungs. Luckily it's also heavy so it settles quickly and cleans up well with a good quality Shopvac fitted with a hepa filter.
And lest I scare you off with warnings of how much work it is... It's totally worth it!
James