I used several visuall-diff-editors whit the several version-control software and i currently use Meld: it’s gtk, has in-line edition ( let’s you change the working copy with a real-time diff computing ) and its “command line diff” and diff3 compatible which makes it work smoothly with version-control software.

So, for the both version-control systems that i use currently here is my setup

SVN

For a quick diff using meld just run:

$ svn diff--diff-cmd meld

For a permanent setup edit ~/.subversion/config and set the diff-cmd to meld

GIT

Write a small wrapper:

#!/usr/bin/env sh
meld $2 $5

and the just configure svn to use the wrapper as diff tool

git config --global diff.external /path/to/wrapper