Only changes from i7 to sandybridge are listed below..
Sandy Bridge DT (LGA 1155) will be a direct replacement for Core i5/i7 LGA 1156, but I doubt whether the owner of the latter would bother too much with the upgrade since the only notable differences are :
(1) a few new instruction sets, the most notable being AVX, that will still require software to be written to take advantage of them-probably around the two-year timeframe for AVX usage to become anything more than a novelty
(2) native SATA 6Gb support, as opposed to a third party onboard controller chip.
(3) Upgraded DMI (4 lanes PCI-E v2.0 for "Southbridge" duties)
The new chipset retains the dual channel DDR3-1333 (official support) and sixteen lanes of PCI-E 2.0 that the P55 enjoys.
So, LGA 1366/X58 will remain the enthusiast setup of choice* until Sandy Bridge B2 (LGA 2011) launches in late 2011.

* Depending upon whether Bulldozer mounts any worthwhile challenge, assuming it launches before LGA 2011....not a given at this stage.


Would really love to see how their native 6gb support scales to the gimmicky current third party onboard controllers?