Apparently if you are looking to overclock, ivy bridge retail stepping is a much hotter chip. What this means is that you will not hit as high overclocks upgrading from a sandy bridge 2700k to the 3770k. The difference in overclockability outweighs the IPC increase, and therefore these two chips are nearly equivalent at maximum overclock.
The bottom line is, unless your planning on running stock, or to overclock with L2N, these chips are a BIG side-grade from sandy bridge. What makes this worse is the price of the new ivybridge chips will be in the 350+ USD dollar range, which for only a few more dollars will get you a significantly more powerful and overclockable i7 3930k by then.
Remember how the i7 2600k smoked the 980x in many tests? Dont expect this with ivy bridge against current E series processors. Ivy bridge will be a worse jump from sandy bridge, than any intel CPU jump in history.
In Pro-Intel OBR's own words, "Ivy Bridge E1 are total shit! Do not buy them! "
In other news, Vishera looks on track and will be released mid third quarter. (September) This is AMD's chance to prove themselves. If power consumption and heat are significantly reduced, expect drastic increases in overclockability, which is AMD's speciality.