I have tile down to my countertops in most of my kitchen, so no 4 inch backsplash. I sooo want to redoo my countertops and backsplash and hopefully I will soon. The backsplash tiles are the cheap 4x4 white ceramic tiles that you can get at any big box store (builder installed). They have held up pretty well, but the grout is starting to get a bit hard to clean (it looks kind of dingy) and the silicone between the countertop and the end of the tile is cracked across the whole length of my counter. It doesn't look like there's any water damage there yet (especially behind the sink), but I think it's just a matter of time. There is one small corner of my kitchen where the builder did put the 4 inch backsplash, probably as an afterthought as it is a separate piece of laminate attached to the counter. I hate that backsplash! It gets dusty and takes up uneccessary space. I also think the no backsplash look is a much cleaner, neater look.

Construction adhesive will get brittle over time. Also, you're actually lucky that oils from the adhesive didn't bleed into the stone and discolor it. As for using mastic for the slate, from a technical standpoint, it's not adviseable, for the same reasons, as well as the fact that it'll take alot longer to dry. Now from the personal standpoint-- for one 4" row, I don't see a problem with it. Additionally, although I've seen many problems with lighter colored stones, I've yet to ever see mastic "bleed" thru slate. You'll just have to let it sit a day or so longer to harden up well before you grout, and when you DO grout, be careful that the pieces don't move.

My granite supplier advised using tile from the granite up (no granite back splash). She could have advised the other way and made a little more money, so I think she advised based on her honest opinion. I also like the "no granite back splash" look better. Just guessing, I'd say the only reason to use the 4" granite back splash would be if you weren't going to use any other back splash at all (a more low-budget option, in my opinion).

Have you considered wallpaper? You can bring in color, as well as a design, if that's your 'schtick'. Just throwing another consideration in the mix. I personally *hate* a backsplast covered in tile or granite from countertop to bottom of cabinets, or even further up. I've gone *about* 3/4 up the wall, with the remained just the neutral color thruout the rest of my home, but only on the interior cabs, so above the stove and sink areas. On the perimeter bank of cabinets, it's just a painted wall, where I had planned to use wallpaper, but haven't done so yet. I also picked up at an auction a painted canvass, which is long and narrow, and thought of using it here. It's a vintage French scene of a girl feeding chickens in a barn, done in dark colors, which is my preference. I just don't want to leave it should I sell. ;)