Just to add – with regards to the question of "whether you need it to work in IE", you need to consider whether the text is readably without the shadow/outline.
If you've got white text on a white background, but you use text-shadow to give it an outline and make the letters visible then you definitely need to put something in place for IE-users (whether you go for a scripted solution or a different stylesheet that puts the text in a different colour).
On the other hand, if you've got sufficient contrast between the text and the background that it will be visible without the text-shadow then it just comes down to aesthetics – how much do you care about IE users seeing the page exactly as you intended it? Or can they make do with the letters plain and unadorned? That's up to you.