PS None of these scripts work perfectly due to browser-specific quirks.
PPS Some people worry that these scripts violate the programs' terms of service. Click loggers do not modify any ad code, and they work passively. YMMV, IANAL, ETC.
Shawn's does not work with Firefox, so you will be missing a bit of stats while using his. There isn't a script yet that I've seen (SEO Book claimed to have one, but it doesn't work.. I also tried coding onto the one they provide, but it still didn't work) that works with Firefox.