GNOME 2.x is being phased out. In Ubuntu, they're rolling their own new UI centred around Unity, whereas pretty much every other distro is going to GNOME 3. Both of these require graphical acceleration, but provide unaccelerated fallback modes. The reason for the change seems to have two primary motivators: acceleration by default, and a desktop environment UI overhaul.

The whole Linuxy world is up in arms about the changes.

Contra

Many others have commented on various aspects of this new world order.

jwz vs gnome-screensaver

jwz moans about the lack of a screensaver. His main argument is:

(Note that Zawinski has a vested interest in screensavers existing.)

I wracked my brain and could not come up with a use case for screensavers in this day and age, except a very few special circumstances. The original purpose of screensavers was not to entertain with a slide show or a Game of Life simulator, but a hack to avoid CRT burn-in in lieu of actually turning off the monitor when not in use. Now that we've all switched to LCDs, which both don't have a burn-in problem and are able to be turned off or suspended in software, they're obsolete. The point of a new major version is to cut out the obsolete cruft, which is exactly what's happening, so bravo GNOME 3.