One of the advantages that the binary graphics drivers from ATI and NVIDIA have over the open-source drivers is a much easier driver installation process. When using either company's binary driver, you generally just download a single Linux package from the vendor's website, run that package, use the vendor's auto-configuration utility, and then restart the system. Sure, sometimes you may need to obtain an extra dependency for your distribution or may run into an ABI compatibility problem if the driver doesn't support the latest bleeding-edge version of X.Org or the Linux kernel, but generally it's a straight forward process.
In order to use the GMA X4500/X4500HD under Linux, you will need to use the just-released xf86-video-intel 2.4.0 driver for mode-setting, 2D, and video support and then the latest Mesa code for the OpenGL acceleration. The GMA X4500 support was just added to Mesa a few weeks back and isn't even in a released version yet. The next version of Mesa where this Intel support will arrive is Mesa 7.1 and will come in tandem with X.Org 7.4. Even when using released versions of these packages, telling a new user to obtain the needed build dependencies, build the package from source, and then configure the setup manually isn't an ideal situation. When the support you are after isn't even in a released version, the user now needs to go through checking out the latest source-code from the git master of the respective revision control trees. The process of obtaining hardware support via an open-source driver for a brand new piece of hardware isn't exactly easy right now to a new user, especially when it comes to the graphics side of Linux.
Aside from Fedora and a few other distributions, these new packages won't be pushed into most distribution package repositories until they are readying a next major release. For instance, Ubuntu users will need to wait until October with Ubuntu 8.10 "Intrepid Ibex" before the latest Mesa / Intel code appear and thus "out of the box" support for these Intel IGPs. The latest development release of Ubuntu 8.10 (Alpha 3) is still too old for the GMA X4500/X4500HD support. However, using Ubuntu 8.10 Alpha 3 we had built the latest xf86-video-intel DDX, Mesa, and DRM (Direct Rendering Manager) code from the respective git master branches.
In addition to using the git code from xf86-video-intel/DRM/Mesa (checked out on the morning of July 28), we were using the Linux 2.6.26 kernel and X Server 1.5.0 RC5 (v126.96.36.1995). Our test system consisted of the Super Micro C2SEA G45 motherboard, 2GB of OCZ DDR3-1333 memory, Intel Core 2 Duo E8400 processor @ 3.00GHz, CoolJag LGA-775 server heatsink, and Western Digital 160GB SATA 2.0 hard drive. The monitor used was an Acer P243WAid 24" LCD at 1920 x 1200 and we were using its HDMI interface.