Probably you can, but you have never done it because you have a shiny interface for everything. I'm talking about this discovery of mine:

svn diff | kompare -

What it does is to take the output from svn diff and pipe it into Kompare, a merge/diff utility from the KDE Project. I can do this from the command line, straight from the directory that I'm in, and bang! I get a nice graphical overview, complete with the tree structure that I can navigate to see what I'm about to commit. Honestly, this little command gets me excited everytime I run it.