And how will it improve other GTK themes such as Ambiance or Elementary?
Best Answer
The GTK+ 3 release notes gave the basics of it.
GTK+ 3.x will not directly change/improve themes like Ambiance, in fact, most of these themes won't work as yet, as they have to be ported.
However, you can expect to see some improvements all around as things progress with GTK+ 3.x.
*This answer is now outdated, and needs an update.
The problem with implementing rgba currently is lying with the applications that run on the gtk+ library. However, with the switch to gtk+ 3 it is likely that Ubuntu will inherit this feature as a default option.
I'm sorry I don't have a link to hand, but the feature was not dropped, just hindered.
EDIT:Here is a link that indicates the possibility of rgba as a feature of gtk3 (which Ubuntu uses as of 11.10).
GTK+ 3.0 will be available for 11.04, but not included by default and none of the default applications will be built with gtk3. This will give application developers time to port to gtk3, theme engines and themes to be updated, etc.
Best Answer
The GTK+ 3 release notes gave the basics of it. GTK+ 3.x will not directly change/improve themes like Ambiance, in fact, most of these themes won't work as yet, as they have to be ported.
However, you can expect to see some improvements all around as things progress with GTK+ 3.x.
*This answer is now outdated, and needs an update.