The To filter can be very handy, for example if the spammers use BCC, and your email doesn't show up in the To list. Or, with a combination of using the [email protected] trick, it can be used to catch very specific messages and filter them.

Sadly Gmail filters lack the ability to differentiate between To, CC and BCC. With those, you can do some really handy filtering in office environments to make sure only stuff sent directly to you hits the inbox. Other stuff can sit in a less distracting folder for later reading.