I do not have any first-hand experience with the technology, but I will be looking for this feature when I buy my Ultrabook. According to the Intel® AT page the technology is built into the hardware in such a way that formatting or switching the hard drive will not bypass or block the poison pill. Check out the Intel® Anti-Theft Technology Demo Animation.
What you said is true, but only after the kill pill has been sent. At that point it does not matter what the thief does. It is too late. My concern is actually sending the kill pill. If the Thief is smart, he will immediately shut down the os if the computer is on. He will then start up your computer with a live ubuntu disk or USB drive and pick all the sensitive documents off your hard drive. No need to connect to the internet to do that. If the computer is already off, it just saves him the trouble. As long as he doesn't connect to the internet, the kill pill can not do its job.
After that, do a clean whip of the OS and WALA! The kill pill can no longer be sent to the cpu. It no longer has the software to do so if the OS has been whipped clean. Keep in mind, all of this is previous to the kill pill being sent. After it is sent, everything I just said is invalid.
The only thing that could invalidate what I just said is if somehow the kill pill can be sent to the cpu via internet without some kind of software. I don't see how that's possible. That kill-pill-command has to go through some kind of code to get to the cpu. If that code isn't native to the OS, which I doubt it is (even if it is it can't be native to EVERY OS), then the kill pill is very software and very OS dependent, and is therefore fundamentally insecure.
The only way to get around this is if you have an 3G card internal to the laptop. The 3G card slot is hardwired to the cpu. This way Intel can send a kill pill command via an SMS text message. And this has to be a 3G card that support Intel AT 3.0. This is the only way that I know of the that kill pill can be sent independent of the OS. It is all outlined in this document.
One may say a thief will more than likely not think of the possibility of the computer having Intel AT. But as this technology becomes more popular thieves will become more careful.
Receiving the kill pill is not at all dependant on the OS, but you are right that an outside connection is needed to receive the kill pill. No matter how the laptop is booted, once it is connected, the poison pill can be received making the laptop useless to thieves.
I think anyone with data on the hard drive that is valuable to thieves should consider fulldrive encryption. It is no secret that Intel uses full drive eencryption on laptops to prevent data theft. The deployment planning and implementation is described in the paper http://i.dell.com/sites/content/business/smb/en/Documents/Deploying-Full-DiskEncryption.pdf.