If you are looking into leveraging the Sun IPS technology + Update center tool, I suggest that you check out the nice (Confluence-based) wiki at http://wikis.sun.com/display/IpsBestPractices/Image+Packaging+System+Best+Practices.
One thing I am looking at for IzPack is to provide a deep (yet optional) IPS integration through dedicated panels and the possibility to have some online packages that would be delivered by IPS…