Where do browsers stand with XML now?

[webmasterbeta]

I've started creating websites again and was shocked the other day when I saw a college students site that was all XML and it worked good in both FF and IE. It didn't do much and it was for one of his classes but I didn't know the browsers could handle XML decently at all.

So how well do FF and IE handle XML?

I see people writing about using CSS for XML pages but does XSL work with them now, too?

Is it still too early to think about creating an all XML site?