A very impressive card indeed, with a price point in the region £350 Inc. VAT that matches GTX 580 1.5GB pricing and this card matches one for performance but has two bonuses. More memory which makes it more future proof and better for high-res gaming, but even more importantly just like the 7970 these cards are hugely overclockable.
Clocking the 7950 at NDAMHz core and NDAMHz memory which they all do with ease (with the Asus BIOS), you have a stock 7970 performing card for considerably less money. Unfortunately it does seem like its not possible to unlock the shaders and as we've seen the 7970 is a true overclocking demond.
So in essence the maximum stable overclock I achieved was NDAMHz Core and NDAMHz memory using the Asus BIOS. Using that same BIOS on a 7970 were talking around 1225-1255MHz Core and 7500-7800Mhz memory. Though remember the 7970 has the full 2048 shaders which gives a decent performance boost.
All in all the 7950 is approx 30% cheaper than the 7970 but when flashed and overclocked its only about 10-15% slower. The 7970 is faster and definetely has a better cooler without doubt, plus a more quieter cooler too, that really helps to keep the case temperatures down, wheras 7950 coolers just heat your case up. So it still stands if you want the best buy the 7970.
Overall the 7950 is great value for money, against an overclocked GTX 580 3GB the 7950 when overclocked is faster in benchmarks and its overclocked game performance should be at least on par with an overclocked GTX 580 3GB gaming performance, so as the card cost less than a 580 3GB, the 7950 is good value.