I am working on a social kiosk project which modifies on Firefox. We have used an early version of this system in some Mozilla events in Brazil where you can check a video of the used template here -
http://www.vimeo.com/tag:tagvisor. This uses the Web model ( read XML, CSS, RSS feed, SVG, HTML etc... ) all in client side for the presentation parts. The main challenges we are facing ( as now we work to put this at one of the computer science department of University of Sao Paulo in Brazil ) now are related to stability so that it works 24x7. At this point, we have modified an Ubuntu OS to boot without the graphics manager ( so now mouse etc ) and then it launches a Firefox in full screen. This Firefox has a controller extension in it. This extension puts the Kiosk Mode to function and our goal is to improve the management aspects - so that you can control this Firefox remotelly as this is intended for many terminals. We decided to go with full firefox + an extension so that we can take advantage of a full Mozilla system, with plugin and some updates, and yet we can limit Firefox user interface functions so that popups do not appear, updates are queued for later etc.