This idea has derived from this one:
http://brainstorm.ubuntu.com/idea/12379/ and the comments posted on it.
Upon installation of Ubuntu, you should be able to select what applications you want / need and what applications you don't want installed. This has two big advantages, from my point of view:
1. There's less disk space use -- more free space! Also, by copying lesser files to the hard disk, the installation could be quicker.
2. It offers the user more flexibility and choice. For example: someone could choose to have Thunderbird installed by default, instead of Evolution (in the GUI I imagine it like this: Install an Email Client -> List of Email clients to choose from). That would spare them the chore of uninstalling Evolution and installing Thunderbird by default (just an example).
3. Because the packages are on the CD, if the user decides later on he wants some application, he just pops the Ubuntu CD in and installs it. This spares him the download of packages from the net, which may be a pain if the user is on dial-up.
The GUI could also have some "Profiles" like "Default" -- the default Ubuntu instalation, "Minimal" -- no apps besides the GUI, "Office" -- All OO.o apps, Evolution, etc...