My 2 cents:
I'm currently working on a web-based Java application. We have a build server (Hudson) which does not have access to the command-line subversion executable; instead, it ships with a pure-java Subversion library, to be able to access the repo before pulling the sources to build the app.
Now we needed the build process to include the global revision number in the app home page (pretty much like StackOverflow does, if you look at the bottom-right corner of your screen).
Unfortunately there are no good integrations between Subversion and Ant. The best one, SVNAnt, is more targeted at using the command line svn.exe and has given us quite some trouble to run.
In the end, it took me two hours to use SVNKit, which is a pure-java library for Subversion access, to tweak our build script to look at the revision number and insert it in our files.
Personally, I can't see what's so hard about creating a variable, say, $GlobalRev$
that you would insert in each file, just like you do with $Id$
or $Rev$