Broadwell is shaping up to be very exciting for the 14nm processor itself and the many graphics improvements. It doesn't look like Broadwell will ship now until Q4'2014, but it should have great open-source support when it arrives. There's working support found in Linux 3.14 and Mesa 10.1 but it will be improved over the releases to come.
Hitting Mesa Git today for Mesa 10.2 were the following interesting commits:
- Enable HiZ on Broadwell and HiZ resolves.
- Enable fast depth clears on Broadwell.
There's also other i965 driver changes happening on an almost daily basis inside Mesa.