At this point in time I would wait for Ivy Bridge benchmarks. I expect a relatively small increase in performance of around 6% - 8% assuming same clock speed.
Temps for Ivy Bridge will be higher though since the surface area of the CPU is smaller compared to Sandy Bridge. Smaller surface area means less efficient heat transfer to the heatsink.
April 29th. Socket 1155. Priced similarly as Sandy Bridge CPUs unless there shortages for some reason; then all bets are off since e-tailers/retailers will likely charge a premium (Intel will not see even $0.01 of that premium so no need to blame them for price gouging).