I just installed #Trisquel 8 (#Flidas) onto a USB key (8GB USB 2.0) for the first time, and mounted my user file partition as /home. Just to clarify, I'm not talking about a "live disk", made by copying an installer .ISO and making it bootable. I've had to make those to install #GNU #Linux to the internal drive since I got this PC, as it has no CD-ROM drive. I actually ran the installer and installed to a second USB, and so far it's working well.
More details here about how the decisions to install to USB came about, and how it's working out.