My understanding is that a lot of new X11 features (such as XRandR, GEM memory managment, kernel mode-setting and so forth) are added to the core and to the open-source drivers, and closed-source drivers lag behind significantly. Also, I've a friend with an nVidia-based laptop, and suspend/resume apparently works about one time in ten, while it worked flawlessly on my Intel-based laptop.

Also, apart from the Paulsbro/GMA500 fiasco (which was contracted out to a third party), all Intel's graphics hardware has had open-source drivers written by Intel themselves, so it doesn't seem too extreme to expect similar support for Larrabee.