I've seen it done with vitreous before...what type of glass tile inserts are you planning? As long as it doesn't get heavy use (things banging down on it), it should be o.k., from what I've seen.

I have glass tiles on the wall and solid glass for a countertop. You could do stone tiles with glass inserts but I would prefer to avoid any grout on a countertop. Ultimately the grout gets dirty and a burden to keep clean. The solid glass counter is very easy to maintain.

You could carry the shower wall design to an accent wall eg. behind the vanity and use the glass inserts there to tie the two areas together.

My comment would be close to Flyleft's. Just like glazed tile, not all glass tile is as impervious to scratching as the next. Make sure that the glass you want to use for the countertop will not scratch easily.