Marc Weintraub, writing for PeopleSoft Apps Strategy:
The new PeopleSoft delivery model enabled by the PeopleSoft Update Manager (PUM), means the continuous delivery of enhancements and maintenance via PeopleSoft Update Images. In order to assist customer who are deploying PeopleSoft 9.2 and ensure they get the latest and greatest capabilities the PeopleSoft team periodically plans on delivering Revision Releases. Revision Releases are a recut of the CDs for PeopleSoft 9.2 that include enhancements and maintenance through the most current PeopleSoft Update Image. Upgrade scripts are updated so that the Revision Release is the scripts target. What this means is customers who are just starting their upgrade or implementation of PeopleSoft 9.2 process can go directly to the latest PeopleSoft Update Image.
Great info. More details here. Check it out.