Thanks so much yifanlu! I just snagged this and installed it a minute ago. I figured I'd share a little trick for fellow Mac users to make the timing easier. Instead of dragging the update file to your device, you can use terminal to copy the file and eject the kindle in one go. First, with the Kindle attached to your computer in USB mode, open a Terminal window and type "mount" (without quotes) and hit return. This will give you a list of all the disks mounted in your system, one of which should be /Volumes/Kindle. There should be a line like this:
/dev/disk4s1 on /Volumes/Kindle (msdos, local, nodev, nosuid, noowners)
the /dev/disk4s1 part is what we're after. Now type "cp " (note the space) and drag the update file for your device into the terminal window. This will copy its filename into the window. Then, without pressing return, type " /Volumes/Kindle && diskutil eject /dev/disk4s1" (but be sure to use the disk you found earlier with the mount command).
The full command should look like this:
cp /path/to/my/update_jailbreak_0.5_etc_etc.bin /Volumes/Kindle && diskutil eject /dev/mydiskname
Don't press return yet, just leave that window open and eject your kindle and unplug it. Restart it and plug in the USB cable while it's restarting. Click on the terminal window to make it active, but leave a finder window open so you can see the sidebar, or make sure you can see the desktop. As soon as the Kindle drive icon appears, hit return. The kindle's screen should immediately go blank, and you can immediately press menu. When the screen refreshes, the menu should be showing and you can go into settings, press menu again and update the kindle.
That's probably needlessly complicated, but using it I was able to successfully apply the hack while holding a baby in one hand
Also, I'm not sure if this made a difference, but I had a lot of books and lots of collections, so I made a backup of my documents folder and my collections.json and then deleted them from the device. I think that it failed the first couple of times because scanning the collections was spawning a bunch of new processes and the pid of the update process was outside the range allowed in the jailbreak. Anyway, once I deleted my stuff and used the terminal trick, it worked great.