ARS Technica decided to overclock the AMD Phenom II X4 940 processor from 3GHz to 4.2GHz to answer the question whether the architecture will scale to provide continued competition for Intel's Nehalem. You can check out the article over here.
We've known from the start that Phenom II would primarily target Core 2 Quad processors rather than Core i7. AMD definitely hit its target; Phenom II compares well against Intel's 45nm Yorkfield processors. A Phenom II X4 940 (3GHz) is currently $229 at Newegg while the Phenom II X4 920 (2.8GHz) is $195. Intel currently offers the Q9400 (2.66GHz, 6MB L2) at $229, the older 65nm Q6600 Kentsfield at 2.4GHz at $194.99, and the Q8300 (2.5GHz, 4MB L2) at $189.99. All of the Core i7 parts are significantly more expensive than the Phenom II X4 940; the Core i7 920 is $294.99 while the 940 is $565.
So how much bang does Phenom give for the buck?
The reporter concludes that while Deneb is great for gaming right now, AMD definitely has a long-term problem it's not going to be able to solve with clockspeed alone. He noticed the 4.2GHz Phenom II wasn't always able to outperform the cheapest Core i7, the 2.67GHz Core i7 920, much less the top-end 3.2GHz Core i7 965.