XML differencing anyone?

Curious if anyone has any experience with XML differencing, especially 
on an Apache server.  I've been looking at the Perl modules like 
XML::SemanticDiff, XML::Diff, and XML::DifferenceMarkup, but they all 
seem to have some slight limitations.  I just realized it might be 
possible for me to set up a Java servlet to run some of the Java-based 
XML differencing programs, but from what I've read so far many of them 
seem to be even worse off (slower, eat more memory, etc.).  What would 
you all suggest I use and why?  Any help would be greatly appreciated!

Thanks in advance,
Chris