I'm writing this to let you know that I've found "bug" in the Dashboard widget iStat. It's not a bug per se, but you should know about it.
iStat offers many statistics about your Mac -- amount of time running since reboot, temperature, fan speed, etc, etc. However, if you choose the option of listing currently running processes in iStat, after a few seconds, it starts the program lsof. This program sucks up about 98% of your CPU cycles, so your Mac might be slower. (It also might not, but of course running your CPU more than you need to is a waste of heat and power, especially on a laptop.) Quiting iStat does not quit lsof, however, so the process will keep running until either your reboot, or you quit it manually with the Unix tool kill.
iStat shows the process lsof only some of the time. I monitored it using ps -aux. Below you can see what lsof is doing to my cpu after I listed processes with iStat. My fans on my MacBook are getting louder and louder as I type this, and pretty soon I'll have to reboot.....
Oh any by the way iStat temperature monitor and fan speed doesn't work on MacBooks.
You have been warned!