PCI Express v3.0 is where most the magic from Ivy Bridge comes from IMHO.
- Yes the CPU is generally better than the Sandy Bridge but the delta between the 2000 series and 3000 series isn't huge.
I'm expecting Haswell to be more integrated with Intel Thunderbolt technology and still have PCI Express v3.0.
It might be +15% better at IPC per clock, just to really stick it to AMD's micro-architecture --- keeping it 3 years behind Intel.
It will include AVX2, which will really put AMD at a disadvantage however I don't think it'll be used by much until new updates for Windows 8 are released.
http://en.wikipedia.org/wiki/Haswell_%28microarchitecture%29
It may even be ~ +17.5% faster per clock over Sandy/Ivy Bridge, if the cache is going to be redesigned then it will keep performance higher during heavier workloads and it looks like it will definitely have more (visible) registers.