Check the DAZ Studio Discussions forum at DAZ  -there was a long thread on glass, and there have been some more recent discussions. One thing that emerged is that it depends on the lighting - it was hard, going on impossible, to get settings that looked good in all situations. With rflection and refraction it's important to have something to rflect and refract in the scene - a glass object sitting on a plain surface in an otherwise empty scene won't do much.