Having used Gmail for months, the one feature it has that I wish were present in other email applications is the ability to seamlessly mesh all of the email in a conversation, including the email that the user sends. In other words, if I reply to someone, that reply is stored and displayed along with the message that I sent, making it easy to follow the flow of the conversation. I’m glad to see I’m not the only Thunderbird user interested in this feature, as indicated by Bugzilla cases containing the word conversation. I’m not sure any of the open cases accurately describe what makes the Gmail representation of email conversations nice, though.