The rpi-renderer is better than the current gl-renderer and should be better for the hardware although it's not as flexible.
Beyond introducing this new renderer, there's some general Weston changes too. One of the new features introduced by the set of eighteen patches is a exposay mode for providing a window overview mode with animated transitions. The patches also provide a new optional keyboard-focus animation for dimming unfoucsed surfaces.
These Wayland/Weston improvements were done by Collabora in conjunction with the Raspberry Pi Foundation for showing off the Linux desktop capabilities of this low-cost ARMv6 development board.
The set of eighteen patches to improve Wayland/Weston can be found on the Wayland development list.