Nice looking.
The only drawback to glass tile is to understand that, when you get calcium scale on it, you can not use conventional blasting techniques to remove the scale or else you will “frost” (scratch) the glass. Many tile cleaning outfits use simple glass bead blasting to remove scale from tiles and that will easily damage glass. Chemical treatments can remove scale but they are slow and labor intensive.
So, as waterline tile, I personally would not want to use glass because it’s going to get scale and then you’ve got an expensive clean up to do. However, for some, the aesthetics of glass will trump any technical issue so, to that end, it’s a personal choice.