The bottle is made form a robust plastic, I have both the 0.5L and the 1L and have had them in hard service for over a year with no complaints.
I read elsewhere people mentioning leaks from the top, I don't believe their experiencing a leak as such, the top retains a tiny amount of meths after you close it that can subsequently come out onto your hands. It's best to shake this `big drip' out of the bottle after you use it (away from people or tents).
Other tips worth noting, if the bottle has been heated (by the sun) since it was filled be careful when opening it as the meths will have pressurised and may spit as the pressure equalises (this is also why you shouldn't fill above the marked line).
When re-filling the bottle, if the lid is hard to twist off do not be tempted to use a pen or similar object through the tie point of the lid to give mechanical advantage to force the lid off, I've seen a number of bottles with the tie point snapped off presumably from doing this. Loosen the lid by gentle tapping.
These should not be considered to be criticisms of an excellent product, just additional operating advice.