I already sent you the ajax snippet by mail and I informed you I didn't get the peeps out of the module. When debugging I also couldn't find where the error was, until I commented some of the checks. Then I found we actually had two errors in what we typed during the tutorial.
This changeset contains what we added during the tutorial + the two fixes.
Hope you can use it. I thought a pull request would be the easiest way for you to review, if you haven't already fixed it yourself. And it's a good exercise for me on using git and github.
working JSON example