One data point is not enough to form an opinion about clock speed and voltage. There are so many variables that go in to what Vcore you need to get a stable clock, that you have to look over several different thorough reviews in order to gain a consensus. That is the only way to minimize the effect of the array of variables, such as mobo, RAM, user error, etc.
The reach the same conclusion as most people are predicting, which is that those with a 4770k should hold off, particularly if they can hit 4.4 on air already.
But 4.4 on air is no guarantee for the original Haswell chips, so 4.8ghz would be an achievement by Intel.
On a side note, for the vast majority of people, AVX stress testers are for stability, not a real-world idea of temperature expectations. Even so, 4.8 @ 79C on an unrealistic burn test isn't bad. But why would you switch out the cooler between stock and OC? Far too much variance, I believe.