Thanks to one of you raising the issue, we now have fixed the problem with watchlists. You will need to go to your profile page, watchlist tab and select the interval (hourly, daily, weekly) that you want to receive notification. Then, if you put an item on your watchlist, you will receive notification (via e-mail) when the item changes.
This might be useful for the assignments page, this blog, or pages that you use to coordinate work within your group. You can even watch the whole HCCF2010 space or the whole XWiki, but you probably don't want that much information.
Please feel free to let us know if something isn't working (we're still working on the "Wall" permissions issue).
--hal