While Gnome 1.4.x is an addition release to the existing Gnome 1.x platform, Gnome 2.x is a major change:
It is the port of the whole Gnome platform from GTK 1.2.x to GTK 2.x.
It removes old cruft such as imlib and libgnorba and all the deprecated features of libgnomeui. It cleans up all the libraries' APIs, based on user feedback. It integrates the new libraries in the core of the development platform.
The diagram below shows both the desintegration of the previously monolitic gnome-libs package and the integration of the new libraries in the platform.
The above-mentioned changes introduce a number of important user-visible changes:
The font API abstraction of Pango is implemented using freetype or the new (better :) Xft or even plain X API. This means transparent antialised/hinted font display for the users.
ATK, the Accessible ToolKit, defines an API which exports accessible information to accessibility-related applications: this means that thanks to the GTK implementation of the ATK interfaces, all GTK applications become accessible.
gnome-vfs' integration means that users should be able to open files independently of their location and this is transparent to the application author.
The use of GConf to store a lot of the parameters of some widgets in libbonoboui and libgnomeui means that user changes to these preferences are dynamically applied in all the applications which use these widgets (the look of toolbars for example).