QEMU 2.5 features new ARM capabilities, improvements to MIPS R6 emulation, a new TileGX target, various Intel instruction set extension changes, support for new Intel memory instructions, Xen support for pass-through of Intel integrated GPUs, VirtIO improvements, support for multi-queue networking with vhost-user, support for network filters, record/replay support for TCG, and a ton of other improvements and new additions.
Besides the Intel XenGT pass-through support now working with upstream QEMU 2.5, there's another big graphics-related change... In fact, it's the feature I am most excited about with QEMU 2.5. With this release is now the support for interfacing with the VirtIO 3D GPU support for allowing accelerated OpenGL via guests. This support though must be used in tandem with the Linux 4.4 and Mesa 11.1+.
More details on QEMU 2.5 can be found via the change-log and the big release can be downloaded from QEMU.org.