i like it, it's light and elegant. it uses virustotal and will kill anything that fails analysis. i think jotti might be better, as virustotal has some crap AVs on there that throw up a lot of false positives, so crystal will then overreact b/c virustotal overreacted. perhaps if the crystal developer allowed us to change a setting so there had to be 2 or 3 virustotal detections to count as a crystal detection. it's not a big deal though, you can just allow it.
anyway, it is really really easy to play with, just download the portable. turn it off if you're installing or updating something, cuz it might kill it. and the developer has a thread here on MalwareTips with a lot of dialogue. i'm too lazy to look it up for ya, lol.