The AVX programming guide has been updated with info about new extensions:
http://software.intel.com/file/36945
That should double integer SIMD throughput on those upgraded instructions.
Haswell is also getting a hardware random number generator.
http://software.intel.com/file/36945
1.4 OVERVIEW AVX2
AVX2 extends Intel AVX by promoting most of the 128-bit SIMD integer instructions
with 256-bit numeric processing capabilities. AVX2 instructions follow the same
programming model as AVX instructions.
In addition, AVX2 provide enhanced functionalities for broadcast/permute operations
on data elements, vector shift instructions with variable-shift count per data
element, and instructions to fetch non-contiguous data elements from memory.
That should double integer SIMD throughput on those upgraded instructions.
Haswell is also getting a hardware random number generator.