Currently the LXDE desktop provides a nice alternative to full desktops like Gnome and KDE. It's much lighter on resources, behaves more like a traditional desktop is expected to, and doesn't get in the user's way.
I'm glad to see LXDE among the supported desktops on Mageia 2, but it seems to me that it needs a bit of TLC. Thus, my list of stuff in the default LXDE install that I think could be changed...
The Oxygen GTK engine could be replaced. Oxygen looks rather nice and works on GTK2, GTK3, and Qt; but it's also very slow - e.g. it makes drop-down menus and window resizing lag, when they're instant with other theme engines. I think a better alternative might be to use the Xfce theme engines for GTK2 and GTK3, and install libgnomeui as well so that Qt programs can match those themes.
Xscreensaver should be running and usable by default. This one is probably a bug: the xscreensaver daemon doesn't start with the desktop, and there's no keybinding or button to lock the screen. This is easy enough for a knowledgeable user to fix, but it would be better to have it working in the default setup.
The default application selection could IMO be better. For instance, Empathy already includes GStreamer and GTK3, so Xine-UI could probably be replaced with the more familiar Totem without wasting too much space. And there doesn't seem to be any CD/DVD burning software installed by default; Brasero would probably work fine, since (again) most of the dependencies would be dragged in already by Totem, GThumb, and Empathy. Also, there's no PDF reader in the default install - epdfview or Evince, or even Xpdf, would be a good addition.
Mageia with LXDE is pretty usable as is, right now; I just think it needs a bit more polish to match Gnome or KDE in terms of usability. Hopefully my feedback on this is useful.