Last week, I triggered the apt-distupgrade on both my 
Ubuntu laptops which effectively downloaded Ubuntu 13.04 (“Raring Ringtail”) to these machines. This was actually sort of unexpected as I haven’t been really following Ubuntu’s latest efforts. I’m aware of Canonical’s push to the mobile market: their case to bring Ubuntu to cellphones and other devices received high praise in the media. That is, if Canonical can deliver on speed (UI) and speed (Roadmap).
The reason why I bring up Ubuntu Touch is that Canonical is aware of the slugginess of their current Unity interface. I’m pretty certain I brought this up in an earlier post (when I installed/upgraded to 11.10): it’s by default, a memory hog. What keeps me switching back to KDE or say, Gnome 3 is that Unity is heavily supported by Canonical. This is the main reason what keeps me away from other Ubuntu-descendants like Mint.
Anyway, what I mean to say is that 13.04 is supposed to be having most of the optimizations of Ubuntu Touch. As the release notes say:
Unity 7 brings a lot of performance improvements, reduced memory consumption and a great number of small UI fixes to bring a better overall shell experience.
Unity does feel like it has been improved (besides the fancy new icons for apps and the changes to the launcher): memory wise, I can’t tell the difference. It just generally still feels bloated. Time permitting, I’ll check out Gnome’s state at a later stage.
Update 1: Rebooted back in Gnome 3 and my first impression is that Gnome desktop takes a lot less memory than Unity.