The issue with updating the open-source graphics driver stack on Windows is that it's much more inter-weaved than using the proprietary graphics drivers on Linux or Windows. With the proprietary drivers, there is just one blob to fit into the system. For the open-source Linux graphics drivers, pieces of the driver are found within Mesa, the Linux kernel, the DRM library, and an individual X.Org DDX component. The actual stack can be much larger than that too depending upon if the driver needs updates to LLVM, VDPAU, VA-API, or other X/Wayland/Mesa components.
Updating one component can mean needing to update the other components due to API/ABI breakage, new internal dependencies, or not being able to have full hardware support / functionality without updating all pieces of the puzzle. When upgrading the entire Linux kernel, that can also be a big issue since it affects all areas of the system for potential breakage or regression and just not the graphics driver.
For end-users, it's a heck of a lot easier updating/installing the proprietary drivers than having to upgrade the open-source Linux graphics stack and that's why for fixed-point distributions it's not commonly available as an option. Intel OTC, however, announced last week the Intel Linux Graphics Installer. "The aim of this installer is to provide a simple route to getting recently released (12.07 or 2012-Q4 in this case) kernel and userspace packages for i915 family graphics devices."
This Intel driver for now is primarily targeting Fedora 17, Fedora 18, Ubuntu 12.04 LTS, and Ubuntu 12.10. The installer can be triggered from the desktop menu or by launching intel-linux-graphics-installer. What this effectively comes down to though is just a facade for interfacing with apt-get or yum depending upon the distribution for getting updated distribution-specific packages from repositories on Intel's 01.org server.
The components hosted within the Intel driver repository is a new kernel or i915 DKMS module, Mesa, xf86-video-intel, libva, vaapi-driver, cairo, llvm-libs, libwayland, and libdrm.
So unfortunately this installer isn't anything original to fundamentally improve the open-source Linux graphics driver stack by making it easier to update/install the open-source Intel Linux GPU driver. Already for distributions like Fedora and Ubuntu there are commonly independent third party repositories (or Ubuntu Personal Package Archives) for fetching these updated graphics components post-release.
What Intel has now provided is just a convenient installer for setting up those repositories and then updating to the new components in a distribution-specific manner. If you're not on a Fedora or Ubuntu based operating system, you're out of luck with this installer or if you're on a derivative using a different kernel release where the DKMS module would be unsupported or break.
Should you be interested in this installer, visit the 01.org page.