Dialogs should be more informative
"Do you want to install package '%s'?" isn't particularly informative. I'd rather see a much more detailed dialog that explains what you are about to do. Here's a first rough draft of what I'm imagining:
You've opened the following AptURL: apt:wine?
This instructs your package manager to enable the "Universe" repository and install the "wine" package. This software is downloaded from Ubuntu's official software repositories, so it has been thoroughly tested and built specifically for Ubuntu.
Information about the "Universe" repository:
The Universe repository contains software that is maintained by the community, and is not officially supported by Canonical.
Information about the "wine" package:
Microsoft Windows Compatibility Layer (Binary Emulator and Library)
Wine is a compatibility layer for running Windows applications on Linux. Applications are run at full speed without the need of cpu emulation. Wine does not require Microsoft Windows, however it can use native system dll files in place of its own if they are available.
This package includes a program loader for running unmodified Windows executables as well as the Wine project's free version of the Windows API for running programs ported from Windows.
Do you want to do this?
The package information would be the same as shown in Add/Remove, and might be best in a scrollable box. I'm not sure if there's an equivalent cross-distro source for repository descriptions, but it might need to be in a box, too?
I think if the dialogs were well-written, we could enable more dangerous actions like adding third-party repositories as well, and the dialog would contain a big fat warning telling you what you're about to do and how to decide whether it's safe or not. If written well enough, there would be no danger, since people who don't understand what they are doing would be scared away by the dialog. Installing from the Ubuntu repositories should reassure you that it's safe, while installing from a third-party repository would do its best to scare you away.
Also, the dialog can take a long time to pop up. *Something* should pop up immediately as soon as the program is called, and *then* it can do any processing it needs to. "You've opened an AptURL. Please wait while processing the package database..."