As I previously mentioned (though not on the front page), I've installed Ubuntu 12.04 on the CR-48. My process for doing so was a tad bit convoluted, in that I first had to install 10.04 and upgrade to 12.04 because of the hard drive format switch.
I've had 12.04 installed for the better part of a week already, and there is one thing that really sticks out: Unity is a whole lot faster. Not xfce or open-box fast, but Gnome-Shell or Cinnamon running on the same system fast.
I've got the same basic application stack as before, Chrome, Sublime Text 2, Gnome Terminal, Dropbox. I've also got a couple other things installed, Nuvola Player for playing music, and I've started using vim a whole lot more than Sublime Text (though, only on the CR-48, the W520 is still mostly Sublime, with the occasional use of vim).
I'd forgotten how simple Ubuntu makes everything. I don't mean to say that as
a bad thing, but everything is configured out of the box, and I happen to like
most of the defaults (I've really only changed a couple things, my PS1 from
/u@/h:/W $, which displays
don@crunchy:[dirname] $ instead of
don@crunch:[pwd]$, making sudo not require a password (I hate that feature),
and adding a couple aliases that automatically sudo applications for me).
As for Unity, it's pretty much what I remember, but faster. In my own order of Gnome-based desktop environments, it's Cinnamon > Unity > Shell > Fallback. Unity is nice, and functional, but it's really not the DE I want on a computer with a higher resolution (well, if Unity is ported to Arch, I might consider using that, provided Cinnamon still isn't working, but I have a feeling that because more people like Cinnamon, it'll get fixed first).
I really haven't used the HUD, mostly beacuse I'm used to traditional menus. Speaking of menus, global menus are starting to grow on me. I'm not sure about that on a larger screen, but on the smaller 12" screen, it's nice for two reasons: windows take up that much less screen space; and it keeps everything unified.
Compared to Arch, I'd still rather use Arch, but that's because I'm that kind of person, and I don't like having everything decided out of the box, I'd much rather pick it later.
Compared to Mint, I think that, thanks to Unity's speed boost, Ubuntu might take back the Beginner's suggested distro stop.