Apple's Mail.app is beginning to drive me up the wall. Thanks to a bone-headed decision made in the Leopard update, a nearly useless feature has rendered a very useful addon almost as redundant.
For some reason, a UI genius at Apple decided that it would be just spiffing to have the program jump to an email when you hit a key, using the starting letter of the email's subject line as the destination. Unfortunately, the code conflicts with the handy Mail Act-on from Indev. This piece of donationware which comes from the same company that provides the also-handy tool MailTags, lets you assign macros to keystrokes.
I have three key-commands that I use all the time. One shoves press releases into the Releases
bucket folder; one puts emails into the Invitations folder (which is slightly misnamed - it's the folder for everything related to interviews and meetings); and the third does the same but sets a @Waiting tag.
However, since Leopard came out, Mail Act-on now has to fight with the built-in keystroke detector so it works only about 50-60 per cent of the time. On an operating system where you find a lot of add-on software that adheres to the 'wei wu wei' philosophy, this is a real problem. It means having to go back to dragging releases with the mouse or watch the fight between a great little piece of software and some weekend hack that has almost no reason for existing.
You want to see how Mail deals with folders that contain emails from a mailing list - most will start with the same letter. I'm not sure I've figured out the logic of what it does yet.