Depends on the application, of course. Haswell introduced some really cool new instructions (both the Bit Manipulation set as well as the Software Transactional Memory set). Don't have any numbers off-hand, but these can definitely speed up certain workloads.
The transition is more like from SSE2 -> AVX2, in integer workloads. AVX2 adds 256-bit wide integer instructions and gather-instruction. Gather does multiple loads in one instruction.
