Well, I can offer up some qualitative observations: we have two computers side-by-side, my i7-920 @ 4.2 recently upgraded to a GTX780, and my wife's new 4770K, stock clock with my old GTX580. So far in virtually every game (except GW2) my older i7 with the faster GPU puts up higher FPS. This is true in Skyrim, Bioshock Infinite, Far Cry 3 and Metro Last Light (the four games I checked.)
There's no investment regret (she needed a new PC, and the 4770k runs quiet, cool and is very, very fast) but it also convinced me that Ivy-E is my "true" upgrade. Upgrading to Haswell would give me newer chipset subsystems (important) and much less power consumption (important) but I would be delusional to expect a dramatic improvement in compute performance.
There's no investment regret (she needed a new PC, and the 4770k runs quiet, cool and is very, very fast) but it also convinced me that Ivy-E is my "true" upgrade. Upgrading to Haswell would give me newer chipset subsystems (important) and much less power consumption (important) but I would be delusional to expect a dramatic improvement in compute performance.