(Later, I switched IM clients from Adium to InstantBird, which also supports that combination.)
That left Terminal, which I couldn't figure out how to configure to support the same shortcut. Until now.
I'm not sure if it's because I have since upgraded to Mac OS X 10.7 (Lion). I could've sworn I tried something like this back when I wrote that previous blog post, and it didn't work.
- Go to System Preferences > Keyboard > Keyboard Shortcuts > Application Shortcuts.
- Press the + (plus) button.
- Select "Other..." from the Application menu and select Utilities > Terminal from the file picker dialog.
- Enter "Select Next Tab" (without the quotes) into the Menu Title field.
- Focus the Keyboard Shortcut field and press Command + Option + RightArrow to set the keyboard shortcut, which will appear as ⌥⌘→.
- Press the Add button.
Repeat steps 4-6 with "Select Previous Tab" and Command + Option + LeftArrow, which will appear as ⌥⌘←.
Those shortcuts should now work in Terminal.
With this change, all five of my current primary productivity applications on Mac (Firefox, Thunderbird, Instantbird, Komodo, and Terminal) support a consistent pair of keyboard shortcuts for Next/Previous Tab, which are two of the most common commands I issue in all of those apps.