Heterogeneous XML editing environments - how do you cope?

I'm working with people who use a variety of tools to edit XML. Some 
editors, like XMetaL, feel very free with non-significant whitespace, 
providing a user interface that shields the user from the very long 
lines their tool creates. That's a challenge for those of us who come in 
with other tools like Emacs, which shield the user somewhat less from 
the source code.

If I had a tool that would reliably pretty-print the XML source without 
trashing any important whitespace formatting, I'd be fine. Are any such 
tools really reliable enough to be trusted?

How do the rest of you cope with the artifacts of various XML editing 
tools in heterogeneous editing environments?

Jonathan