I don't know about anyone else, but I wouldn't use ShieldsUP! to scan another PC. It only goes after half a dozen ports, which is pretty worthless, if you ask me. Maybe for the newbie user it's good (and that's who it's designed for), but for most technical types there's other scanners out there.
Personally, this is a non-issue to me. I get more port scan generated traffic in five minutes online at home than someone scanning me with shields up for an hour would generate.
