When you create an iOS Application in XCode by default the version of the application is stored in <appname>-Info.plist. It would be really handy to get this in to code for compile time checks and #defines...
If you want visual diff's while developing on OSX using subversion then this page has a good description of how to set it up and some scripts to wrap Apple's FileMerge application to give to nice visual merges/diffs.