Thank you all for your wonderful advice. We decided to call the tile guy early this morning and play it safe and just go with the white grout. I just figured I rather be safe than sorry! : ) I will try to post pictures tomorrow of the longest kitchen remodel in history, almost two years, but who is counting, besides me! Thanks again for all your advise~

Guest bathroom shower surround, glossy white tiles, "regular" TEC grout, 2008 I think. MB and hall bathroom tub surrounds, glossy white tiles, TEC XT grout, 2011. No issues. The XT grout doesn't require sealing, but can be, using a solvent based sealer. We have moderately hard water. We wipe down the tub surrounds with a microfiber cloth after showering (to prevent water spots on the glossy tile). I clean the bathrooms pretty much weekly. I spray the tub surrounds with 7th Generation disinfecting bathroom cleaner spray. Let sit a few minutes, and wipe dry with a microfiber cloth. Tile and grout look as they did when first installed.

I would use white caulk in the corners, not gray. This is because the tile layout should look like the tiles bend around the corners. i.e., half a tile on either side of the corner, or 1/4 on one side and 3/4 on the other side. So a contrasting caulk would cut the tile visually and eliminate the illusion of the bending tile. Also, always caulk, not grout, when you have changes of plane. Finally, as others mentioned, you should not have slivers of tile on the ends or corners. You fix this by shifting the tiles. So on the RH side (I assume this is your first photo), the pattern should be shifted 1/2" to the left, so that in the corner you have full tiles or half tiles, every other row. Then on the left corner the tiles will all be pushed down 1/2" so that the wrapped around portion that's now about 1" becomes 1 1/2" wide.

agree with previous posters..simple tile-blend the grout, as similar to the tile as possible..unless you deliberately want high contrast grout to accentuate it for some reason. then it becomes a decorative element on its own, and needs to be considered as such. more rustic tile that has different shape, like say star and cross mosaics, or lantern shape, etc-you want then a grout that's just a tad different in terms of shade, so it won't blend with the tile to the extent the effect of shape will be lost