@harishankar
What You mean by that?integrated ACPI power management
Exacly the same effects can be achieved by creating ~/.gtkrc-2.0 file with your settings, example here: http://strony.toya.net.pl/~vermaden/text/dot.fonts.confnice(r) anti-aliased fonts
I already have everything that I need started by ~/.xinitrc file, but maybe some people need to make it automatic as they will often left 'unfinished bussiness' on their desktopssession management
These can be used the same without GNOME.screensavers
Explain?convenient menus
If, for example, I would be running low on disk space?notifications
This can be achieved by sysutils/hald itselt or FreeBSD's amd(8) daemon, GNOME has nothing to do here.auto-mounting
You do not gain anything by going that way, for example, GTK2 applications would not 'behave' or run faster if you will run whole desktop environment based on GTK2, but it may be the opposite in special circumstances, like running low on memory (or while doing CPU intensive tasks) then low memory footprint window manager like openbox will be a lot faster then metacity with all other GNOME 'peripherals'.Besides since I use so many Gnome/GTK programs I prefer to run Gnome directly.
Disk space is the least important factor here (cause we also have these dependencies installed to run GTK2 apps), all these daemon/notifications/icons/automounting/anything consumes memory and CPU, but if you feel more comfortable in full desktop environment then just cut to minimum personal applications, then its ok.Like I said, I could probably work from a minimal desktop, but why bother? I have the disk space and pulling in Gnome actually takes care of a lot of dependencies for applications that I later install.
As time has passed XFCE became lighter GNOME, its not all that light anymore, but LXDE on the other hand is still very light and fast.Having said that, I think Xfce is a great compromise as well. Lighter than Gnome, reasonably featureful.