Given that moderate speed production systems are throttling, I see Intel as being in a very bad place. There is essentially no margin for thermal error, even in moderate speed systems. Where can they go from here?
The most impressive evidence is that they flushed their whole desktop and server roadmap a few months ago. They wouldn't have done that unless they were convinced that the current P4 (Prescott/Nocona) design was hopeless.
Seeing throttling in moderate speed production systems confirms it. Imagine one of these systems with the case on it and a year's worth of dust accumulation on the fans, vents, and heatsinks.
Dell has already had to replace cooked motherboards in a number of their Northwood based small form factor P4 systems - imagine what will happen with Prescott!