Really? I've been pretty unhappy with it on mine. The large, permanent top bar, the enormous window chrome, combined with the miserable vertical screen real estate on my netbook are all... aggravating. The performance on Atom's GPU is also erratic and often multi-second laggy (though it's much better than 3.0 was).
I wound up switching to KDE, which has... strange characteristics, but window management is butter smooth, like you might hope for in 2012. About as smooth as it was before everyone switched to compositing.
Are we talking about the same Gnome 3? Mine has a thin toolbar for the clock, and all the other UI is hidden unless you mouse over the top left corner. It works extremely well on the comparatively small MacBook Pro 13", to the point that I'm now seeking the best linux distro to offer as close to vanilla Gnome 3 experience as possible.
The vertical space occupied by the top bar and title bar on my box (not a netbook) is 58 pixels. Honestly I suspect that's the lowest vertical overhead among mainstream desktops, though I don't have a copy of Unity running next to it to check. Certainly the OS X Dock and Windows 7 start bar are much bigger.
I just measured! Gnome 3 is about 58 pixels, KDE is about 50. But the bar is on the bottom and hides, which means in practice there's just 20px of chrome in the way.
I wound up switching to KDE, which has... strange characteristics, but window management is butter smooth, like you might hope for in 2012. About as smooth as it was before everyone switched to compositing.