I am using XUbuntu 11.10 with XFCE and am willing to give Unity a try, but don't want to loose my well-tuned system and desktop. I don't think LiveCD is what I need: I want to try the behaviour of applications missing on it. What should I do? Can I install Unity, choose a desktop environment in some config file, reboot and get Unity, then set it back, reboot, and get XFCE?
you can install a desktop interface for example gnome3 like so
and you can choose it from the login screen which desktop interface you want to use.
to install unity search for unity in the software-center or run this in the gnome-terminal
OK, I take no more credit than simply finding this via Google, but the following XFCE on Ubuntu 12.04 instructions might help you (NB. this is probably best viewed at the original site, due to highlighting):
Click on the grey Ubuntu logo (Dash home), in the top of the side panel. Use the query Terminal Click on Terminal
Type (use copy/paste, that's safer):
Press Enter. Type your password. Your password will remain entirely invisible. not even dots will show, this is normal. Press Enter again.
Now an intensive operation is being launched; simply wait.
B. Log in to Xubuntu
First: the Great Cleanup!
Type (use copy/paste, that's both easier and safer):
Press Enter. Type your password. Your password will remain entirely invisible, not even dots will show, this is normal. Press Enter again.
Then, when it's finished, in the terminal (copy/paste): gksudo leafpad /etc/lightdm/lightdm.conf
In the text file that opens, you'll see the following line (the last one): user-session=
Change it into: user-session=xubuntu
Save the file and close it.
This completes the transition: your Ubuntu has almost entirely been turned into Xubuntu!
D. Beautify and tweak Xubuntu
Tips on beautifying and tweaking Xubuntu can be @ https://sites.google.com/site/easylinuxtipsproject/xubuntu.