I just watched the presentation on Feature Packs:
This article is a follow up from a first article that lists some of the new features provided via feature packs.
The one thing that I learned is that Feature Packs are more for people installing new versions of PeopleSoft whether a new customer converting to PeopleSoft or an existing customer upgrading to the latest version. If you are keeping current on bundles you also get the new features.
So, the important thing in my opinion is to create a business process that can quickly install and test the bundles so that you keep your system updated. This allows you to both avoid problems by getting fixes in and allows you to take full advantage of system with the new features.