From what I've read the i7 4770 (the part just below the new 4790 they've released today) is about 10% faster than the 3770 which in turn is about 10% faster than the 2600 from 2011 (I have the 2600K).
So if that's correct if I upgraded my PC to this platform I'd be looking at maybe a 20-30% boost in CPU speed (1.1 * 1.1 = 1.21 then top that up a bit to allow for chipset improvements etc).
My current CPU is already blisteringly fast and for all but the most extreme tasks is going to show no difference at all from these new chips. This is a 3 year old CPU.
So I really don't see any reason to get too worked up about these new chips compared to the older ones. The really exciting thing about them is the reduced power consumption - but that applies most in devices like ultrabooks rather than desktop PCs.