So yesterday I learned via several posts here that #NetBSD has a persistent live USB image for x86-64. Seems to work pretty much like you'd hope: find out right away if your hardware works, kick the tires for a bit without committing to a full install, try it on different machines if you have options. Log in as root, run startx, and it's like a fresh install. Only odd thing is an extra remote after resizing to use the whole USB stick. It's like a throwback to Knoppix CDs of old. (But those weren't persistent; you can actually install packages and stuff on this and they stick around)