They are wonderful looking when installed!  I have old walls and on the first try did not use any extra adhesive.  What happened was when the walls started to expand and collapse due to normal humidity I lost a few of the tiles.  So... I got smarter and used Loctite (recommended by Aspect) and redid my small DYI project.  Now, I have purchased more tile and am currently working a much bigger DIY project - tiling my bathroom!  Again, they really look great when installed.