Version:            (using KDE 4.4.1)
OS:                Linux
Installed from:    Ubuntu Packages

** Bug Description **
If an application is the sole window open on the screen, its animations are smooth (minimize, restore, fade-in and fade-out).  However, if another window is already open in the background, then the foreground's window's animations are noticeably choppier.

** Reproducing the bug **
1) Open two instances of Dolphin; we'll call them "Dolphin A" and "Dolphin B".
2) Resize Dolphin A to be around 50-60% horizontal and 50-60% vertical respective to the screen's width.
3) Maximize Dolphin B, and then minimize it.
4) Repeatedly minimize and restore Dolphin A (there should be no other windows showing on-screen).  Note how smooth the animation is.
5) Now, restore the maximized Dolphin B.
6) Repeatedly minimize and restore Dolphin A with Dolphin B sitting behind it on-screen.  On my system the minimize/restore animation of Dolphin A is noticeably more choppy.

** Enabled Compositing Effects **
For your reference, here are the effects that I have enabled: Invert, Zoom, Fade, Login, Logout, Minimize Animation, Shadow, Slide, Taskbar Thumbnails, Translucency, Dialog Parent, Dim Screen for Administrator Mode, Box Switch.

** /etc/X11/xorg.conf **
Section "Module"
    Load           "glx"
EndSection

Section "Device"
    Identifier     "Configured Video Device"
    Driver         "nvidia"
EndSection

Section "Screen"
    Identifier     "Default Screen"
    Device         "Configured Video Device"
    Monitor        "Configured Monitor"
    DefaultDepth    24
    Option         "NoLogo" "true"
    Option         "RenderAccel" "true"
    Option         "TwinView" "false"
    Option         "AddARGBGLXVisuals" "true"
    Option         "UseEvents" "false"
    Option         "TripleBuffer" "1"
    Option         "DamageEvents" "1"
    Option         "InitialPixmapPlacement" "2"
    Option         "BackingStore" "1"
    Option         "PixmapCacheSize" "70000"
    Option         "OnDemandVBlankInterrupts" "true"

    SubSection     "Display"
        Depth       24
        Modes      "1280x960" "1152x864" "1024x768" "800x600" "640x480"
    EndSubSection
    SubSection     "Display"
        Depth       16
        Modes      "1280x960" "1152x864" "1024x768" "800x600" "640x480"
    EndSubSection
    SubSection     "Display"
        Depth       8
        Modes      "1280x960" "1152x864" "1024x768" "800x600" "640x480"
    EndSubSection
EndSection

Section "Extensions"
    Option "Composite" "Enable"
EndSection

** My System **
Motherboard: MSI K9N SLI Platinum (nForce 570 SLI chipset)
CPU: AMD Athlon(tm) 64 Processor 4000+ (2.6 GHz)
RAM: 2GB DDR2
Video: Dell NVIDIA GeForce 7800 GTX w/ 256 MB RAM (PCI Express)
OS: Kubuntu 9.10 i386 (with KDE SC 4.4.1)
Linux Kernel: 2.6.31-9-rt
NVIDIA driver: 185.18.36
Screen Resolution: 1280 x 960
X.org: 7.4
Qt version: 4.6.1