Lets see...
- Virtually unbreakable potion flasks
- Virtually unbreakable lenses (glasses, spyglasses, etc.)
- Virtually unbreakable windows
- Arms & armor not susceptible to rusting, most acids, heat metal spells...and extremely fashionable, to boot.
- Arms & armor that are difficult to see in wet/snowy/icy conditions (ever find glasssteel caltrops in the river with your feet?)
- Shields that let you maintain LoS
- Expands the list of arms & armor usable by Druids