I can't login/Flint says it can't find any Campfire accounts
Flint authenticates using your 37signals id. This should be the same username and password you use to log in to Campfire currently. To make sure you're using the right username/password, log in to https://launchpad.37signals.com. You should be able to log in there, and see your Campfire room(s) listed. If you're unable to log in there, Flint won't be unable to authenticate you either.
What are mention keywords?
These are words that you want highlighted specially in Flint. You might enter your name or initials, or maybe another word you always want to know when someone mentions. If a message matches any of these words, Flint will show the message blue. You can also use these words to restrict what message you get notifications for.
Where do I set the user avatars?
All the user avatars come directly from Campfire. Each user must set their own avatar. You can set yours by logging into Campfire, clicking "My Info" in the top right next, and then clicking "Edit your personal information".
How can I auto-complete user names?
In Flint 1.1, you can start typing one or a few letters of a user's name, and hit the tab key to bring up a menu of all the user's that are currently in the room that start with those letters. When the menu is visible, you can hit space to insert that user's name. If the completion is done at the beginning of the message, it will include a trailing ":". You can also hit tab without typing any letters to get a list of all users in the room, and just choose one.
How do I use emoji?
Campfire supports emoji by entering specific codes that get translated into emoji when posted. There is a complete list of emoji available at http://emoji-cheat-sheet.com. You can type in those codes, and Flint will automatically convert them to their emoji. If you start typing an emoji code, you can hit tab to autocomplete so you don't have to remember the name. You can also insert emoji directly into Flint using the 10.7 special characters (Edit > Special Characters) feature. If the emoji is supported by Campfire, it will be automatically converted to the correct code.
My trial expired and I can't install from the Mac App Store
I've heard from a few users about issues when installing from the app store after the trial expired. This seems to be a cache issue between the Mac App Store and OS X. First thing to try is to quit MAS, then delete all copies of Flint from /Applications, and try to reinstall from the Purchases tab. If that still doesn't work, (after ensuring there are no copies of Flint in /Applications), reboot your computer, and try to reinstall from the app store. So far, in every case a reboot has ultimately fixed it.
Sorry for the inconvenience, I'm looking for a way to prevent this in the future.