For me coming from an e8400 it a no brainer especially since same price point, but yeah I don't see why people on SB would upgrade since it only a tick+
This is interesting though:
Clock for clock, Ivy Bridge (which is a "Tick" on Intel's roadmap) does offer performance improvements over Sandy Bridge, albeit mostly in single digit percentages. This is good news as the new processors will directly replace the old ones at roughly the same price points.
From the large pool of CPUs that we have tested/binned, Ivy Bridge uses 25% less power on average clock for clock due to the lower voltages required (in this case Sandy's 1.48v to Ivy's 1.27v).
Ivy Bridge's on-die temperatures (TJ Max of 105 degrees celsius) are a lot higher than Sandy Bridge, indicating possible high electrical leakage on the new process or a different measurement method. Note: Temperatures != Power, although there is some correlation.
Ivy Bridge is a (subzero) overclocker's wet dream, able to hit core frequencies near 7GHz with no cold bugs (unless motherboard induced).
In general, Z77 boards are better made and engineered (shorter electrical traces, better component placement) than their P67/Z68 predecessors, doing away with niggling BIOS firmware bugs and dodgy VRM implementations.