M[io][cn][ro]... man

Indeed; converting from GNOME to XFCE would yield memory saving for most users: the average
GNOME user probably runs several non-GTK+/GNOME applications: Firefox, Thunderbird, and OOo.
Thunderbird consumes the same amount of RAM within or without GNOME; Firefox consumes less
because the GNOME integration won't be loaded.

You'll be saacrificing the convenience of several GNOME tools -- keyboard management (layout
manager, multimedia keyboards, and shortcut handling are very nicely executed in GNOME), but
power users with tight memory budgets would find XFCe just fine.

I'm a bit concerned about the seeming lack of activity on their web pages and developer blogs,
though...