Well they were to ship today, and many people received notices for 3/10. This would mean that there is some kind of delay. These are the first people that ordered after the keynote. I mean all it could mean is a shortage of a certain part for some machines, but it could also be Apple not being able to fill their order quotas. I personally think that its an issue with the platform that is gonna send everyone back. I expect everyone with a later ship date to get a notice of the push back on or before their shipdate. I can't really think of much else that could add 1 month to people's shipdate, unless like I said it was only certain models that were affected, such as not enough 7200 rpm HD's or such.
edit: and none were shipped today....