I would vote for this for sure.
I have been using Netbeans for a couple of months at work and one of the only things that I do like about it is the way that it highlights changes based on Subversion data. When I’m working on a file I can see which lines do not match the most recent update in my directory. Not asking for something that advanced (though it would be nice) but something that shows which lines have been changed since the file was opened would be VERY gratefully received. I’m currently using v9 but this is one of those things that I think need implementing and would definitely upgrade to v10 if it was only available in that :D