When I enable Desktop Effects in Gnome I experience annoying slow-down of window scrolling (e.g. a web page or OpenOffice document). The only way to get rid of the issue I found is to disable Desktop Effects.

Here you can find a recording of the issue: 
http:http://www.gorzkiepole.pl/video/recording.mp4 or 
//www.gorzkiepole.pl/video/recording.avi

My laptop is HP 530, video card is Intel 945 GM, 3D enabled.
# uname -a
Linux portatilgris 2.6.25.11-0.1-pae #1 SMP 2008-07-13 20:48:28 +0200 i686 i686 i386 GNU/Linux

My xorg.conf:
-------------
Section "ServerFlags"
  Option       "AIGLX" "on"
  Option       "AllowMouseOpenFail" "on"
  Option       "ZapWarning" "on"
EndSection

Section "Module"
  Load         "extmod"
  Load         "type1"
  Load         "glx"
  Load         "freetype"
  Load         "dbe"
  Load         "dri"
EndSection

Section "Monitor"
  DisplaySize  331 207
  HorizSync    30-62
  Identifier   "Monitor[0]"
  ModelName    "LGPHILIPSLCD LCD MONITOR"
  Option       "DPMS"
  Option       "PreferredMode" "1280x800"
  VendorName   "LPL"
  VertRefresh  43-60
  UseModes     "Modes[0]"
EndSection


Section "Modes"
  Identifier   "Modes[0]"
EndSection


Section "Screen"
  DefaultDepth 24
  SubSection "Display"
    Depth      15
    Modes      "1280x800" "1280x768" "1280x720" "1024x768" "1280x600" "1024x600" "800x600" "768x576" "640x480" 
  EndSubSection
  SubSection "Display"
    Depth      16
    Modes      "1280x800" "1280x768" "1280x720" "1024x768" "1280x600" "1024x600" "800x600" "768x576" "640x480" 
  EndSubSection
  SubSection "Display"
    Depth      24
    Modes      "1280x800" "1280x768" "1280x720" "1024x768" "1280x600" "1024x600" "800x600" "768x576" "640x480" 
  EndSubSection
  SubSection "Display"
    Depth      8
    Modes      "1280x800" "1280x768" "1280x720" "1024x768" "1280x600" "1024x600" "800x600" "768x576" "640x480" 
  EndSubSection
  Device       "Device[0]"
  Identifier   "Screen[0]"
  Monitor      "Monitor[0]"
EndSection


Section "Device"
  BoardName    "945 GM"
  BusID        "0:2:0"
  Driver       "intel"
  Identifier   "Device[0]"
  Option       "monitor-LVDS" "Monitor[0]"
  Screen       0
  VendorName   "Intel"
EndSection

Section "ServerLayout"
  Identifier   "Layout[all]"
  InputDevice  "Keyboard[0]" "CoreKeyboard"
  InputDevice  "Mouse[1]" "CorePointer"
  Option       "Clone" "off"
  Option       "Xinerama" "off"
  Screen       "Screen[0]"
EndSection

Section "DRI"
    Group      "video"
    Mode       0660
EndSection

Section "Extensions"
  Option       "Composite" "on"
EndSection