X.Org on NetBSD - the state of things
There are a lot of differences from how NetBSD and the typical distributor ship X.Org. For one, we ship it as an optional monolithic package rather than separate individual packages. This means every driver is included on every system, rather than as an optional module. Sometimes, this means we need to fine-tune driver selection to ensure the correct drivers are loaded on the correct hardware, since multiple conflicting drivers can claim a video output. We also want sensible fallbacks, since if you're using a GPU from the future with an old OS version, you probably want X to seamlessly fall back to a regular framebuffer.
Secondly, the way our "xsrc" repository is set up, it's effectively functioning as a fork of X.Org that regularly pulls from upstream freedesktop.org (but does not push back). This allows X development to happen as part of NetBSD.
Thirdly, we use our own build system based purely on BSD makefiles, not X.Org's based on GNU autotools. This fits well with our build.sh cross-compilation system.
We have a number of drivers which have not made their way upstream. Perhaps the most ubiquitous of these is xf86-input-ws, a driver which came from OpenBSD, targets an API fom NetBSD, and continues to be developed in both. This is a generic input driver that can support any pointing device that the kernel supports. Unlike xf86-input-mouse, it doesn't assume the device is a mouse, and can support advanced touchpad and touchscreen features. Other NetBSD exclusives include xf86-video-pnozz, xf86-video-mgx, and xf86-video-crime. While these all share the "xf86" name inherited from the historical XFree86 distribution, none of them are exclusively for x86.
There are a number of drivers that are accelerated when used in NetBSD, but the acceleration support is missing upstream. This is mostly due to the work of macallan@, who has diligently worked on drivers for accelerators found on SPARC and PowerPC hardware.