The new DRM/KMS driver for the Linux 3.17 release is the STI KMS driver for STMicroelectronics with their STIH416 and STIH407 chipsets. Nouveau is missing out on changes for this pull request due to Ben Skeggs still tracking down a longstanding Nouveau issue but he's expected to send in a separate Nouveau pull request in the days ahead that will have the new improvements for the open-source NVIDIA driver.
Among the core DRM improvements are the start of DisplayPort Multi-Stream handling (DP MST), universal cursor planes, and render nodes support is enabled by default.
When it comes to the Intel driver, we've already written about the Intel graphics changes in Linux 3.17 that drop user-space mode-setting harder, offer Broadwell hardware semaphores support, more power management work, improved Cherrytrail support, universal cursor planes support, and many other changes. There's also been Phoronix coverage of the many Radeon DRM changes for Linux 3.17. Big for Radeon in this next kernel release is fixed-up AMD Radeon R9 290 "Hawaii" support. The Radeon driver also has GPU VM improvements, Dynamic Power Management is used for more hardware, etc.
This DRM pull request also has improvements to panel handling, TTM, the Samsung Exynos driver, the Armada driver, NVIDIA Tegra support improvements, new MDP5/ADQ8084 v1.3 hardware enablement for Freedreno's MSM driver, and various other updates. The lengthy DRM pull request for Linux 3.17 sans the Nouveau changes can be found via this mailing list message.