sudo apt-get install xubuntu-desktop or sudo apt-get install lubuntu-desktop
I started with Gnome 3.10 (after ignoring it for most of it's existence except once in the early time) and it failed to register simple mouse clicks in a Steam game (the firs thing I tried). It's also sluggish and ugly and hard to get anything productive done.
So I went to KDE 4.11 next. And it's as ugly as ever. The huge sound indicator at the bottom is just so ugly. And then they have what looks like a Start menu thingy to launch applications. Oh boy, that felt odd. Still miles better than Gnome 3, but nothing I'd like to see on a daily basis.
XFCE is just too bare-bone for me. It's OK in looks, but the task bars are just clumsy.
So I'm probably sticking to Ubuntu for the next LTS cycle too and see what comes of the Unity 8 desktop. Sad to see there are no real contenders.
Also you check out tint2, which is a nice 3rd party panel also used in Crunchbang.
I don't think XFCE is perfect, but it ticks the important boxes for me. So much so that I just use it out of the box now rather than rolling my own from a vanilla OpenBox install (a fun exercise, btw).
Facts: Ubuntu desktop releases are available in a variety of 'flavours' including Lubuntu, Xubuntu and Gnome Ubuntu. The Kubuntu release has external sponsorship from Blue Systems. There is also UbuntuStudio that packages a lot of music/sound/graphics/video applications with a slightly remodelled XFCE4 UI. LTS status is limited to 3 years for the 'flavours' as opposed to 5 years for the Unity based Ubuntu, still one year overlap with the next LTS.
You can, as go8z says, install a range of desktop sessions on stock Ubuntu, but you do end up with a certain amount of duplication e.g. power manager, mousepad/Abiword and gedit/LibreOffice &c.
Plenty of choice so we can get our work done. It is all here...