I am using Arch linux with xorg X Server 1.6.3.901 (1.6.4 RC 1). I have nVidia [GeForce2 MX/MX 400] (rev b2) (32MB RAM) video card using the proprietary nvidia-96.43.13-1 driver.

The problem is with the low 2D performance. Window moving is very slow, I can see the desktop icons refreshing slowly.
During window movement X server consumes 55% of CPU time (in top utility).

I think it is DE independent, because I tried out both XFCE and LXDE. Maybe the issue is nvidia driver specific. The 3D performance is good (887 fps in glxgears).

List of installed xorg components:
local/xf86-input-evdev 2.2.5-1 [0,11 MB] (xorg-input-drivers)
    X.org evdev input driver
local/xf86-video-vesa 2.2.0-1 [0,08 MB] (xorg xorg-video-drivers)
    X.org vesa video driver
local/xorg-apps 7.4-2 [1,85 MB]
    Various X.Org applications
local/xorg-font-utils 7.4-3 [0,49 MB]
    X.Org font utilities
local/xorg-fonts-100dpi 1.0.1-2 [16,85 MB] (xorg)
    X.org 100dpi fonts
local/xorg-fonts-75dpi 1.0.1-2 [15,59 MB] (xorg)
    X.org 75dpi fonts
local/xorg-fonts-alias 1.0.1-2 [0,06 MB]
    X.org font alias files
local/xorg-fonts-encodings 1.0.2-3 [0,80 MB]
    X.org font encoding files
local/xorg-fonts-misc 1.0.0-4 [8,03 MB]
    X.org misc fonts
local/xorg-res-utils 1.0.3-3 [0,18 MB] (xorg)
    X.Org X11 resource utilities
local/xorg-server 1.6.3.901-1 [9,74 MB] (xorg)
    X.Org X servers
local/xorg-server-utils 7.4-7 [0,51 MB] (xorg)
    X.Org utilities required by xorg-server
local/xorg-twm 1.0.4-3 [0,23 MB] (xorg)
    Tab Window Manager for the X Window System
local/xorg-utils 7.4-4 [0,34 MB] (xorg)
    Collection of client utilities used to query the X server
local/xorg-xauth 1.0.3-1 [0,07 MB]
    X.Org authorization settings program
local/xorg-xinit 1.1.1-1 [0,05 MB] (xorg)
    X.Org initialisation program
local/xorg-xkb-utils 7.4-2 [0,34 MB]
    X.org keyboard utilities
local/xterm 246-1 [0,50 MB] (xorg)
    X Terminal Emulator