Intel 64-bit Announcements at IDF
Like them or not, this is a really strong strategic move for Intel. AMD played its hand in the open the entire time, while Intel waited to time its announcement until just after the Opteron launch.
Now corporate shops will hesitate to commit to AMDs 64-bit chip because of speculation about whether its instruction set will be compatible with Intel's.
Pair that with Microsoft's delayed 64-bit Windows launch, and you've got another well played round from Intel.
It's likely that this was only a contingency plan, though. I'm sure Intel would have liked the world to move to Itanium, but this is their second choice of outcomes. AMD gains some market share for a brief moment, but then potentially has to backpeddle to design Intel compatibility into their already completed 64-bit offering.