Ubuntu 12.04 is an LTS that, although features new additions since Oneiric Ocelot, has been designed, created for stability and precision.
Ubuntu 12.10. the at the moment development Ubuntu version, is to probably feature "abrupt" changes for various apps, directions, user interactions, etc like the already announced indicators' revamping.
Update Manager has been renamed in Quantal Quetzal to Software Updater, introducing, along with the mentioned name, a refreshed look:
- the clickable buttons have been moved to the bottom bar, keeping their differentiations (Settings in the bottom left corner, Check/Close/Install Now grouped at the bottom right corner)
- the update details can be expanded (the default state) and contracted, presenting itself, when contracted, as a "semi" app with a lightweight look (the app remembers its state, meaning, contracting the Software Updater and close it then launch it, it will launch the app in a contracted minimalist state)