Almost off-topic, but I notice a lot of talk about Metacity (which I've known and loved since Gutsy) and the demise of Untity-2D (which I liked, but not loved).
This takes me to my own "real-time" testing of how fast an OS/WM is after I click on something or execute a command (whether via terminal or dash).
First on this bland, but good set of Intel Hardware;
I found that after they dropped "dodge windows" I could quite easily use Unity in 12.04. The speed was good .... no waiting for anything to happenIntel Atom CPU 230 @ 1.60GHz
Intel 82945G/GZ Integrated Graphics Controller (rev 02)
Intel N10/ICH 7 Family High Definition Audio Controller (rev 01)
Realtek RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 02)
2GB DDR2 RAM
With the same hardware in Quantal (aka: 12.10) I found myself twiddling my fingers waiting for things to happen, it really was like dropping back to dial-up from DSL
I tend to blame the combo of Compiz+llvmpipe, but I'm a true dummy so I don't know. The same hardware runs the Ubuntu-GNOME-Remix very well running a standard out-of-box gnome-shell session so I think it's fair to say that Mutter (aka: gnome-wm) is better.
Then using Cinnamon from two different sources I find their fork of Mutter - Muffin - is almost as bad as Ubuntu's Compiz. It seems that Mint has recognized that because they're even talking about a 'fallback-session' for Cinnamon using Openbox!
So, I've tested Ubuntu's version of Compiz, Cinnamon's Muffin WM, and GNOME's own Mutter ................ the winner is ...... hands down ...... Mutter!!!!!!
I can even get the Ubuntu-GNOME-remix to run on this anemic hardware:
VIA C7 CPU @ 1500MHz
VIA CN700/P4M800 Pro/P4M800 CE/VN800 Graphics [S3 UniChrome Pro] (rev 01)
VIA VT8233/A/8235/8237 AC97 Audio Controller (rev 60)
Ethernet controller: VIA Technologies, Inc. VT6102 [Rhine-II] (rev 78)
1GB DDR2 RAM
No doubt the performance is better with plain old Metacity or Openbox, but GNOME's Mutter is the winner against Ubuntu's Compiz and Cinnamon's Muffin.
While some people have their panties in a twist over DE's this is really a war of Window Managers
Maybe it's time to admit the GNOME devs know what they're doing.