As I predicted, took less than a day. That said, if you watch the video you'll see that it's sloooooooooooooowwwwww. I was about to jump on the "see, it does need the hardware" bandwagon as the reasoning, but according to the article:
The issue here is not Siri, but is that a special GPU driver for iPhone 4 is needed; and it is obviously not included in the iPhone 4S binary cache - where the Siri files are located.
I'm not 100% sure if it's just that this driver isn't for the iPhone 4 because Siri is (obviously) designed for the 4S or if there's more going on under the hood. Maybe the extra powerful new GPU processor is taking an offload of more than just some of the graphics for the Siri system and that's the reason that the app is 4S only.
I'm hoping that the smart folks out there will continue on with the project and hopefully get something a bit more usable.