Hardware: Gigabyte GA-880GM-d2h, Radeon HD4250 512 shared VRAM, 4GB RAM total, Phenom x4 965BE (3.4Ghz quad). Everything at stock clock speed and voltages. BIOS flashed to latest stable version FF from Gigabyte.

user@user-GA-880GM-D2H:~$ glxinfo | grep OpenGL
OpenGL vendor string: X.Org
OpenGL renderer string: Gallium 0.4 on AMD RS880
OpenGL version string: 3.0 Mesa 9.1.1
OpenGL shading language version string: 1.30
OpenGL context flags: (none)
OpenGL extensions:
user@user-GA-880GM-D2H:~$ glxinfo | grep render
direct rendering: Yes
OpenGL renderer string: Gallium 0.4 on AMD RS880
    GL_NV_conditional_render, GL_AMD_conservative_depth, 
------------------------------------------------------------

In a default KDE install on Ubuntu: Default settings are Use OpenGL 2 shaders enabled and VSync enabled. In Desktop effects such as translucent background when dragging windows and Minimize Animation, dragging a window results in stuttering movement in the former (the screen does not shift. but the window stutters as if it stops for a second and catches up but it's fast so it looks like a stutter [missing frames?]) and in Minimize animation the window stutters also as the animation takes place. Disabling VSync and OpenGL 2 shaders options, there is still stuttering animation. This seems to be OpenGL specific as XRender compositing provides a smooth experience.

In a Gnome Shell 3.8 install: In previous versions of Gnome Shell, there were jerky animations also. In 3.8, which is what is installed on my computer right now in Ubuntu 13.04, the animations are not ALWAYS noticeably jerky, but sometimes they do jerk when happening, it's noticeable in the animation when switching to a new window from the overview and the window slides in front of the desktop. It does not always jerk but often enough. In glxgears I get 58/59 fps normally, and with glxgears window maximized, it still gives the same frame rate. But when switching between three or four windows, there's a jerk in the animation and it shows up in glxgears as a drop in the fps and it goes down to 50-51 fps and is unable to keep up with the refresh rate. Also, in glxgears, I have noticed that the gears move smoothly but after maximizing them, they run smoothly for some seconds, and then I notice a jerk/stutter in the gears once, and then it runs smoothly again. In Gnome Shell, you will probably not notice the jerks when you first use it, but it's definitely there and is an annoyance for someone who uses it a long time. And the stuttering animations are definitely very noticeable on KDE in a default install with desktop effects.

This is all with no custom Xorg conf. With swbuffersWait 0 in Xorg conf, the stuttering is even more noticeable as ever in Gnome, it seems to me.

This seems to be a driver bug (correct me if I'm wrong, I'm a relative newbie to Linux.), so I'm posting this report here. But this is a major problem that needs to be fixed soon. What user wants to use Linux when the major desktops run with jerky effects.