"When using type within an interface element, it either sits on top (dark 1px drop shadow) or is inset (white 1px drop shadow), it's never at the same surface as a button or widget."
Will have to pay more attention next time I'm doing this.
Now that I think about it, I stick to CSS most of the time and try to keep images to a minimum (front-end optimization is a tough habit to kick), so I may forget this by the time the next occasion arises.
Given that these elements are only eye candy, I don't worry too much that they are invisible on IE and older browsers. Think of it as free candy.
We developers might dismiss 1px drop shadows an unimportant; after all, the "real" application is the code we write. But users make no such distinctions. To them, the interface is the application.