Fortunately there's something we can do about that and that is running the development branch of Slackware Linux called "Current", which is amazingly current. It currently sports Linux 3.8.8, KDE 4.10.2, gtk+ 3.6.4, glibc 2.17 and gcc 4.8.0. Here's a link to the changelogs. In addition it includes the clang compiler as alternative and Patrick Volkerding has recently switched to the distribution to MariaDB instead of continuing to use MySQL due to concerns about Oracle, the new owner.
You couldn't ask for more if you were running Arch Linux. In fact, the entry from 19 April reads like Slackware-Current may be a little too current and hints that downgrading a few packages to saner versions may be in order. Fear not, Slackware always includes config files for several more kernels than the main one distributed and other packages in the testing directory, like an alternative xorg-server-1.14. If Arch is a little too bleeding for you running Slackware-Current may be a good alternative and is not far behind. It is also rolling by nature and usually stable and solid, having undergone careful blending by Mr Volkerding and crew. SlackBuilds are very similar to the AUR user repository and PKGBUILD files and third-party tools are available to manage these more comfortably.
Furthermore, Slackware does not jump on any bandwaggon, and Arch users resentful of having been switched to systemd should take a look too. Not that it wouldn't work, from all I have seen it boots very quickly and that's normally all one cares about on the desktop, but...mumbles something about standards and predictability. Plus, many are not just running desktops and the init system seems well documented, understood, transparent and easy. But let's not go there now.
How to get it?
Of course you could just upgrade if you're already running Slackware 14. Several sites periodically create unofficial iso images from the Current tree. If that one isn't available you still have the choice of downloading the entire tree and creating an image from it, or if that isn't possible, install by pointing to an FTP server or install from another partition. The last one is really fast from an SSD, let me tell you. Documentation is available on the DVD/ in the main directory. USB and PXE install is also supported. Eric Hameleers, for example, provides a script to mirror Current for updates, rsync and then create a new iso, aptly called mirror-slackware-current.sh.
Slackpkg is your friend for upgrading core packages provided by the distribution. After the install has finished we need to uncomment a mirror in /etc/slackpkg/mirrors to update from in future. Or switch it to slackware-current mirror if running 14 at the moment. Only one mirror can be selected at a time. Upgrading from earlier releases is not recommended and will almost certainly go wrong. See here for the full routine if you need to. After updating the package database upgrade-all displays a list of all newly available packages. You can deselect any that should not be upgraded. As this is a rolling branch the kernel and important libraries like glibc are not held back by default and your current kernel will be replaced, so careful, and if you're using Lilo it's a good idea to run it again after the upgrade. I've stayed with a system of around the time when 3.7.10 was in the repo because my wireless chip needs the broadcom-sta driver and I got sick of recompiling it with every kernel update, but apparently the new kernel does not need the proprietary driver any longer. Sometimes it's better to let things shake out and see instead of downgrading again later on and have more work. Remember, it's your call. [Good news, it appears after finally upgrading that 3.8.8 once again works with the firmware provided and does not require the Broadcom driver any longer. Let's hope it will stay that way now.]
And that should be it. SlackBuilds from slackbuilds.org for Slackware 14 are all compiling without problems on Current so far, and with that we have access to a wide range of packages and a truly up to date desktop. If 3.8.8, the latest stable kernel at time of writing, isn't enough for you, feel free to compile 3.9-rc8 for yourself. I would contend that the absolute bleeding edge is counter-productive, even on the desktop. In this sense Slackware-Current is more conservative than Arch, where you just get the latest version of everything down the pipe, without feeling outdated. You may not be running a server, but who wants to mess up their carefully constructed gaming setup with Wine and Steam just because some new version of library x is not compatible or introducing regressions.
Although there's still a big problem with spam I have left comments open on this post to aid discussion, so please feel free with any tips, questions etc.