Yesterday, i upgraded my laptop with the latest updates in -Current (i upgrade the packages which has been published between 20 and 24 October updates). I'm planning to upgrade my desktop also in the next few days when i'm done with my work on Windows. One of the most significant updates between those dates were GIMP 2.4.0. It has new looks due to new Tango icons and it's more consistent than before. The upgrade was as easy as issuing an upgradepkg command and it will take care everything for you.
Please note that GIMP will now create a new directory called .gimp-2.4 in your home directory to save all their settings. When you are satisfied with GIMP 2.4, you may delete your .gimp-2.2 directory to save some space. Next, check your Menu entry. You may have to update/delete unneeded menu entry because the new package also creates a new entry for GIMP. Too bad KDE doesn't have a sorting feature on their menu editor (or it was me who didn't see that feature).
Unfortunately, i forgot to take a screenshot of the latest GIMP 2.4, but it doesn't matter that much. You will have a chance to enjoy GIMP also in the next Slackware release or if you can't wait, you can grab the SlackBuild from Slackware-Current site and then compile it yourself to create installable Slackware package (tgz format). It's a suggested ways instead of using -Current package, since it was build using different environment tools.