Hi John,
I use a 1oz glass cloth on a regular basis, mainly as a protective layer over kevlar (it helps avoid sanding into the kevlar) and also as an efficient weave-filler when using heavier cloths (less fill coats and less sanding necessary). Oh and it's also very helpful when saturating UD-carbon to avoid But let me tell you, it's a real pain to use. It's so light and delicate it's almost impossible to not damage the weave pattern. Just laying it down can be tricky sometimes.

best,
Matt