Latex caulk is exactly what you should do. grout eventually will spall. latex caulk can also be painted if you can't match your color.

OMG your kitchen is beautiful! yes should caulk whereever tile meets another type of material. Home D and Lowes sell grout textured matching caulks where they have the bags of grout

Thank you felixnot!

ladyshadowwalker, thanks for the message. That is kitchenaddict's kitchen, isn't it gorgeous? I will definitely caulk where the tile meets the countertop and where the horizontal tile meets the vertical tile on the sill. But I'm also thinking of caulking instead of grouting on the entire flat/horizontal surface of the sill. Not sure if anyone does that, but I thought it would be easier to maintain...

I really don't think caulk on the rest of that surface would be easier to maintain than a good sealed grout. How much mess is going to get up there, anyway? I've always found caulk to get gross pretty easily relative to well-done grout. Plus caulk can be gouged and peeled fairly easily.

Latex caulk is exactly what you should do. grout eventually will spall. latex caulk can also be painted if you can't match your color.

dee850, thanks for the message, we're planning on sealing the stone, but we're not planning on sealing grout...

FWIW I asked my tile guy about this yesterday and in his opinion, stuff (i.e., countertop slabs) moves and caulk doesn't last forever either. He also cautions that the color, even when from the same company as the grout, is always off a little. So he counsels using grout, and re-doing it periodically as necessary. His opinion after 1000+ kitchens. I don't know how to compare his opinion with another's, just thought I'd pass what I've heard from him along though. I opted for his opinion of grout only. Also, he counsels sealing the grout on the backsplash -- I think someone above suggested not sealing it. I didn't seal grout in our bathrooms and it's grody mega-fast; I regret not sealing it (if I could - not sure with that ceramic tile if I even could have though).

Having experienced both sealed and un-sealed grout, I strongly recommend sealing. It made a huge difference.

Thank you all for your feedback!