The New Plugin Architecture is aimed at reducing the bloat in your app and is welcome addition. You specify the APIs that you need and additional plugins can be installed and removed. The new architecture will help streamline the dependencies in a much more efficient manner as compared to version 2.0.
PhoneGap developers are looking forward to seeing support for more platforms, especially iOS 7. The team confirmed that work on iOS 7 is in progress and the day it is generally available, they will be getting that. Plans for supporting Ubuntu and Firefox OS are also in the works.
One of the key features in this release is the support for Command Line tools. Developers are increasingly asking for CLI tools to help improve their developer workflow and utilize tools that they have been using. Version 3.0 sees a big push in bringing that to the developers via CLI tools. The CLI tool can be installed via the Node Package Manager (npm) and you can now use this common set of scripts to control everything from creating projects, running builds, emulating and also interacting with PhoneGap Build. Even installation of PhoneGap is now via the Node Package Manager.
Brian leRoux, VP at Apache for Apache Cordova has given a detailed interview in which he goes behind the scenes with PhoneGap Release 3.0. For more information, visit PhoneGap 3.0 Documentation.