We have a White Thassos backsplash in our MB, and used White Thassos for the shelves/floors/side walls in the tub and shower surround niches in all three bathrooms. We sealed it using solvent based sealer(s).

In the bathrooms it is holding up very well against stains. I was a little nervous about the niche in the MB--a metal can of shave gel sits right on the marble in the niche. I clean the bathrooms every week generally (sometimes pushing it to close to two weeks), and the White Thassos cleans up beautifully, even where the shave gel can sits. Not a mark left behind; no etching or rings either.

We use handmade soaps in the shower (made by local farmer's mkt. and crafts fair vendors). Some of the more colorful soaps leave behind colorful soapy residue on the White Thassos shelves, and those also clean away completely, leaving no stains at all.

FWIW, I use 7th Generation Disinfecting Bathroom Cleaner spray to clean the bathrooms--I spray it on, let it sit for a little while, and then wipe with a microfiber cloth. No rinsing necessary.

HTH