Digit-Life posted an extensive review on the Intel Core 2 Extreme QX9650 Processor which is based on the Yorkfield core:

Supposed power consumption: Despite the claimed 130 W TDP (identical to the QX6850's), the real power consumption of QX9650 equals 76 W at 100% load. It's even lower than that of the 65nm lower-clock QX6700. And even if we consider this value as absolute, 76 W is really low for a top CPU in the series. It's been a long time since we saw a high-end processor not exceeding the symbolic 100-watt line.

Fortunately, they haven't made a Prescott out of a Penryn. At the same core clock the new processor performed 8% faster than the old one (on average). Besides, some details indicate that has been achieved not only due to the extensive approach (e.g., increasing L2 cache volume), but also thanks to the actual speeding up of calculation units. This doesn't make it a new architecture, of course, but the modification is still significant. Given the lower-end products based on this core are available all right, Intel's main rival has a reason to worry. While we still wait for a real AMD K10 in a desktop, Intel's new architecture again surmounts the next performance ridge. If this continues, someone may find their new processors slower than competitor's older ones...