The thing is...all these talks about the "benefits" or "features" of new board, they hardly make any real deference to users (I mean realistically, gamers in general only "need" SATA3, USB3, and whatever "new features" of the new chipset or board, they don't really make any difference other than the "feel good factor" of knowing they have something more (which they don't really need

).
I mean when we talk about 10-20% faster might seem a lot, but when looking at actual CPU benchmarks and frame rate for games, the differences between the i5 2500K and i5 4670K on the same clock is like for example in CPU demanding games, the 2500K does 25fps, and the 4670K does 28fps; and in non-CPU demanding games, the 2500K does 86fps, and the 5670K does 100fps.
As for your point on overclocking, as I said on "average" 4670K it would be 4.5-4.6GHz. So you were lucky enough to land a good chip which can clock to 4.7GHz (or may be even 4.8GHz as you claim), but the same can be said about the 2500K, but their average overclock is 4.6-4.8GHz, and 5GHz is doable if like you someone landed a good chip).
I mean there's no doubt clock for clock the 4670K is faster than the 2500K, but as far as overclocking goes, it's been generally agreed that the 4670K won't clock as high as the 2500K.
Another thing to consider is the the Haswell launch price has creep up comparing to the Sandy launch price from average £160~£170 to £190~£200, most likely due to the lack of competition from AMD's side.