Mechanically more fragile than soda glass, but tougher to temperature shock -- admittedly not that useful for drinking, considering regular mugs also don't often break with boiling water. Good for cooking though: just check out the people mourning these real borosilicate Pyrex measuring cups.
To me it's mostly about the aesthetics. I've broken one or two over five years, but they are just too charming to give up on⦠Light, holds plenty of liquid, and good for pouring from.
