retiling bathroom floor

This is common depending on what was down originally. In some buildings, the tile was set directly in the concrete floor. Impossible to take up the tile without ripping up the actual concrete subfloor. In this case, the new tile is set directly on top of the old and the result is indeed a higher floor. Usually you put in a new threshhold and door to compensate. There should be no problems in the future if the job was done right. Enjoy your new bathroom.

Thanks for your comment, mwade. the floor looks good, so I'll just let it go...

Same story here. Had to rip up part of a bathroom floor to replace pipes. Can't tell it's two layers except for thresholds, no cove at base of walls, and that they tiled around the base of the pedestal sink instead of raising it up the ~3/8". Hadn't even noticed until now.

Biggest issue is usually at the seam between tile and tub, or if you have a "cove" base moulding tile on the walls.