I am curious as to what grout should I use for this [glass mosaic tile]? Do I use a sanded or unsanded grout? Has anyone used the Bostik Dimension grout from My Tile Backsplash?
Sanded vs unsanded has more to do with grout line width. Grout lines < 1/8" are usually unsanded. Grout lines >= 1/8" must be sanded. That said, 1/8" is a cliff hanger and could use either. The problem with wider grout joints is that the grout (cement based, Dimension, being urethane, has a wider range (joints can be between 1/16” - 1/2” in width and at least 1/8” in depth)) can crack as it hardens if it doesn't have sand.
Be sure you go see an installation with Dimension grout. Its reflective proprieties are unique but not for everyone. It would work in a modern or ultra modern style kitchen.
This is really purely design taste. It is a backsplash so water isn't a big deal. If your grout is a much different color than the tile I would go with sanded - if contrasting color go with contrasting textures. If it is similar I would probably go unsanded. Actually last two backsplashes I did with laticrete epoxy. I have to say the epoxy gives a very clean, almost caulk like finish - although harder to put in.