I don't know how it holds up long-term, though some of the guys over on the JB forum swear by it--STT's SB sealer. We used it last year in our new bathrooms on honed travertine, split face mosaic, White Thassos pieces and mosaic, and on our grout (TEC XT grout--not necessary to seal it, but we did). So far everything looks great.
I applied it myself (DH helped over tubs because I couldn't reach that high!). It's very easy to apply and buff off the excess (Porous Plus was a b**ch to buff off the travertine in our guest bathroom--very smudgy and smeary, lots of haze). It has very minimal odor, too which was a big consideration for us, as our bathrooms are tight quarters, and one has no window.
FYI, I ordered a can from John Koessler (he's on the JB forum), who is one of their distributors.
Q