Merging Xcode project files

There are often conflicts in the Xcode project file (Project.xcodeproj/project.pbxproj) when merging branches (I'm using git). Sometimes it's easy, but at times I end up with a corrupt project file and have to revert. In the worst case I have to fix up the project file manually in a second commit (which can be squashed with the previous) by dragging in files etc.

Does anyone have tips for how to handle merge conflicts in big and complex files like the Xcode project file?

EDIT-- Some related questions:

Git and pbxproj

Should I merge .pbxproj files with git using merge=union?

RESOURCES:

http://www.alphaworks.ibm.com/tech/xmldiffmerge

http://www2.informatik.hu-berlin.de/~obecker/XSLT/#merge

http://tdm.berlios.de/3dm/doc/thesis.pdf

http://www.cs.hut.fi/~ctl/3dm/

http://el4j.svn.sourceforge.net/viewvc/el4j/trunk/el4j/framework/modules/xml_merge/