I wonder how much the Android code had to be hacked to make that happen - like, once you jailbreak your iPhone and get Android on there, and Android 2.2 comes out, will you just be able to upgrade and be happy, or will it be essentially a "fun thing to hack around with but not something you'd really want on your primary phone" thing?
I would guess the Linux boot loader will be able to accommodate booting any future ARM6/7 kernels with no trouble. From there it's just a question of drivers. I'm guessing he lifted them from another Android phone using similar hardware. From what I recall everything in the iPhone is pretty vanilla hardware. Those drivers would have to be ported to work on 2.x since that's been one of the major holdups for the 2nd tier Android handsets so far. He also mentions doing some loopback mounts to simulate an SD card. Seems promising for the future.